Switch version from function to string in otelgrpc

[ElenaZvereva]

refactor(otelgrpc): change Version() func to const Version string
Part of #8272

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 82.3%. Comparing base (1139186) to head (03188f1).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##            main   #8317     +/-   ##
=======================================
- Coverage   82.3%   82.3%   -0.1%     
=======================================
  Files        179     178      -1     
  Lines      13695   13693      -2     
=======================================
- Hits       11274   11272      -2     
  Misses      2023    2023             
  Partials     398     398             

Files with missing lines	Coverage Δ
...n/google.golang.org/grpc/otelgrpc/stats_handler.go	98.5% <100.0%> (ø)

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[flc1125]

@ElenaZvereva Please fix the conflict in the CHANGELOG

The requested changes have been applied.