readme: fix example code format

[codecov-commenter]

Codecov Report

Patch coverage: 80.69% and project coverage change: -0.22% :warning:

Comparison is base (e6378f2) 82.51% compared to head (333b587) 82.30%. Report is 7 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #100 +/- ## ========================================== - Coverage 82.51% 82.30% -0.22% ========================================== Files 5 6 +1 Lines 652 842 +190 ========================================== + Hits 538 693 +155 - Misses 84 111 +27 - Partials 30 38 +8 ``` | [Files Changed](https://app.codecov.io/gh/checkpoint-restore/checkpointctl/pull/100?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None) | Coverage Δ | | |---|---|---| | [memparse.go](https://app.codecov.io/gh/checkpoint-restore/checkpointctl/pull/100?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None#diff-bWVtcGFyc2UuZ28=) | `74.82% <74.82%> (ø)` | | | [checkpointctl.go](https://app.codecov.io/gh/checkpoint-restore/checkpointctl/pull/100?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None#diff-Y2hlY2twb2ludGN0bC5nbw==) | `93.48% <94.82%> (+0.38%)` | :arrow_up: | | [tree.go](https://app.codecov.io/gh/checkpoint-restore/checkpointctl/pull/100?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None#diff-dHJlZS5nbw==) | `87.96% <100.00%> (+1.85%)` | :arrow_up: |

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Test Results

46 tests  ±0   46 :heavy_check_mark: ±0   1s :stopwatch: ±0s   1 suites ±0     0 :zzz: ±0    1 files   ±0     0 :x: ±0 

Results for commit 333b587e. ± Comparison against base commit bd9d1a99.