fix: Reduce the amount of memory used by the in-memory extension manager gRPC server buffer

[liorokman]

Noticed that the amount of memory being used for the in-memory extension server buffer was too large due to a typo.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 1 lines in your changes are missing coverage. Please review.

Project coverage is 67.30%. Comparing base (11349b1) to head (4afb999).

Files	Patch %	Lines
internal/extension/registry/extension_manager.go	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3512      +/-   ##
==========================================
- Coverage   67.32%   67.30%   -0.02%     
==========================================
  Files         167      167              
  Lines       20308    20308              
==========================================
- Hits        13672    13669       -3     
- Misses       5643     5645       +2     
- Partials      993      994       +1     

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