issues/341: Return http 404 instead of 400 for bad host header

[komuw]

• This is what example.com and google.com does.

• This also means that we also do not have to pollute logs with it; https://github.com/komuw/ong/blob/46c45d146b6f7277922413fc30de1e4f34f2383c/middleware/log.go#L65-L72

• Fixes: https://github.com/komuw/ong/issues/341

[codecov-commenter]

Codecov Report

Patch coverage: 100.00% and project coverage change: -0.07% :warning:

Comparison is base (46c45d1) 75.05% compared to head (da27694) 74.98%.

:exclamation: Current head da27694 differs from pull request most recent head 620017e. Consider uploading reports for the commit 620017e to get more accurate results

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #346 +/- ## ========================================== - Coverage 75.05% 74.98% -0.07% ========================================== Files 44 44 Lines 4970 4970 ========================================== - Hits 3730 3727 -3 - Misses 993 995 +2 - Partials 247 248 +1 ``` | [Files Changed](https://app.codecov.io/gh/komuw/ong/pull/346?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Komu+Wairagu) | Coverage Δ | | |---|---|---| | [middleware/redirect.go](https://app.codecov.io/gh/komuw/ong/pull/346?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Komu+Wairagu#diff-bWlkZGxld2FyZS9yZWRpcmVjdC5nbw==) | `91.58% <100.00%> (ø)` | | ... and [1 file with indirect coverage changes](https://app.codecov.io/gh/komuw/ong/pull/346/indirect-changes?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Komu+Wairagu)

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