docs: semconv gen: correct the comment on the package containing metrics

[0xdeafcafe]

For example: https://pkg.go.dev/go.opentelemetry.io/otel@v1.36.0/semconv/v1.32.0/genaiconv

The package genaiconv has the following comment:

Package httpconv provides types and functionality for OpenTelemetry semantic conventions in the "gen_ai" namespace.

[linux-foundation-easycla]

• ✅login: 0xdeafcafe / (0aab4df)
• ✅login: 0xdeafcafe / (0aab4df, 3464c29)

The committers listed above are authorized under a signed CLA.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 82.9%. Comparing base (0150494) to head (3464c29).

Additional details and impacted files

@@          Coverage Diff          @@
##            main   #6915   +/-   ##
=====================================
  Coverage   82.9%   82.9%           
=====================================
  Files        261     261           
  Lines      24262   24262           
=====================================
+ Hits       20124   20125    +1     
+ Misses      3761    3760    -1     
  Partials     377     377           

see 1 file with indirect coverage changes

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[dmathieu]

We should regenerate/fix the generated packages as well.