refactor: simplify /health handler

[clambin]

Just check dependencies. No need to report statistics: we have instrumentation for that.

[codecov]

Codecov Report

Attention: Patch coverage is 94.11765% with 1 line in your changes missing coverage. Please review.

Project coverage is 94.23%. Comparing base (bbae5bb) to head (bfe4b3f).
Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
internal/server/handlers.go	94.11%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #61      +/-   ##
==========================================
+ Coverage   92.86%   94.23%   +1.36%     
==========================================
  Files          19       19              
  Lines         701      694       -7     
==========================================
+ Hits          651      654       +3     
+ Misses         41       33       -8     
+ Partials        9        7       -2     

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