remove `swap_refund` in favour of `swap_cancel`

[noot]

These two functions essentially did the same thing, except swap_refund was xmrtaker-only.

[codecov[bot]]

Codecov Report

Patch coverage has no change and project coverage change: +0.19 :tada:

Comparison is base (aa70b55) 54.29% compared to head (525137c) 54.49%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #371 +/- ## ========================================== + Coverage 54.29% 54.49% +0.19% ========================================== Files 93 93 Lines 7967 7931 -36 ========================================== - Hits 4326 4322 -4 + Misses 3097 3064 -33 - Partials 544 545 +1 ``` | [Impacted Files](https://codecov.io/gh/AthanorLabs/atomic-swap/pull/371?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None) | Coverage Δ | | |---|---|---| | [cliutil/utils.go](https://codecov.io/gh/AthanorLabs/atomic-swap/pull/371?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None#diff-Y2xpdXRpbC91dGlscy5nbw==) | `55.55% <ø> (ø)` | | | [cmd/swapd/contract.go](https://codecov.io/gh/AthanorLabs/atomic-swap/pull/371?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None#diff-Y21kL3N3YXBkL2NvbnRyYWN0Lmdv) | `73.21% <ø> (ø)` | | | [cmd/swapd/main.go](https://codecov.io/gh/AthanorLabs/atomic-swap/pull/371?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None#diff-Y21kL3N3YXBkL21haW4uZ28=) | `70.09% <ø> (ø)` | | | [cmd/swapd/profile.go](https://codecov.io/gh/AthanorLabs/atomic-swap/pull/371?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None#diff-Y21kL3N3YXBkL3Byb2ZpbGUuZ28=) | `15.15% <ø> (ø)` | | | [cmd/swapd/signal\_handler.go](https://codecov.io/gh/AthanorLabs/atomic-swap/pull/371?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None#diff-Y21kL3N3YXBkL3NpZ25hbF9oYW5kbGVyLmdv) | `0.00% <ø> (ø)` | | | [coins/coins.go](https://codecov.io/gh/AthanorLabs/atomic-swap/pull/371?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None#diff-Y29pbnMvY29pbnMuZ28=) | `85.61% <ø> (ø)` | | | [coins/common.go](https://codecov.io/gh/AthanorLabs/atomic-swap/pull/371?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None#diff-Y29pbnMvY29tbW9uLmdv) | `100.00% <ø> (ø)` | | | [coins/exchange\_rate.go](https://codecov.io/gh/AthanorLabs/atomic-swap/pull/371?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None#diff-Y29pbnMvZXhjaGFuZ2VfcmF0ZS5nbw==) | `72.72% <ø> (ø)` | | | [coins/exponent.go](https://codecov.io/gh/AthanorLabs/atomic-swap/pull/371?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None#diff-Y29pbnMvZXhwb25lbnQuZ28=) | `100.00% <ø> (ø)` | | | [coins/provides.go](https://codecov.io/gh/AthanorLabs/atomic-swap/pull/371?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None#diff-Y29pbnMvcHJvdmlkZXMuZ28=) | `85.00% <ø> (ø)` | | | ... and [80 more](https://codecov.io/gh/AthanorLabs/atomic-swap/pull/371?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None) | | Help us with your feedback. Take ten seconds to tell us [how you rate us](https://about.codecov.io/nps?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None). Have a feature suggestion? [Share it here.](https://app.codecov.io/gh/feedback/?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None)

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