Fix add_metrics_to_readme.sh script

[satk0]

Link #266
Resolves #269

[codecov]

Codecov Report

Attention: 4 lines in your changes are missing coverage. Please review.

Comparison is base (984c1ee) 99.61% compared to head (184fb0d) 94.52%.
Report is 16 commits behind head on master.

Files	Patch %	Lines
cmd/exporter/main.go	0.00%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #272      +/-   ##
==========================================
- Coverage   99.61%   94.52%   -5.09%     
==========================================
  Files          14       15       +1     
  Lines         774      621     -153     
==========================================
- Hits          771      587     -184     
- Misses          2       34      +32     
+ Partials        1        0       -1     

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