fix(deps): update module google.golang.org/grpc to v1.69.4

[renovate]

This PR contains the following updates:

Package	Change	Age	Adoption	Passing	Confidence
google.golang.org/grpc	v1.69.2 -> v1.69.4

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Release Notes

grpc/grpc-go (google.golang.org/grpc)

v1.69.4: Release 1.69.4

Compare Source

Bug Fixes

• rbac: fix support for :path header matchers, which would previously never successfully match (#​7965).

Documentation

• examples/features/csm_observability: update example client and server to use the helloworld service instead of echo service (#​7945).

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