chore(main): release 2.9.1-SNAPSHOT

[release-please]

🤖 I have created a release beep boop

Updating meta-information for bleeding-edge SNAPSHOT release.

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[suztomo]

 The version for io.grpc:grpc-netty-shaded should be one but there are multiple of them:
io.grpc:grpc-all:jar:1.45.1 / io.grpc:grpc-xds:1.45.1 (compile) / io.grpc:grpc-netty-shaded:1.45.1 (compile),
io.grpc:grpc-googleapis:jar:1.45.1 / io.grpc:grpc-alts:1.45.1 (runtime) / io.grpc:grpc-netty-shaded:1.45.1 (compile), 
io.grpc:grpc-alts:jar:1.45.1 / io.grpc:grpc-netty-shaded:1.45.1 (compile), 
io.grpc:grpc-xds:jar:1.45.1 / io.grpc:grpc-netty-shaded:1.45.1 (compile),
com.google.api:gax-grpc:jar:2.16.0 / io.grpc:grpc-netty-shaded:1.45.1 (runtime),
com.google.cloud:native-image-support:jar:0.12.11 / io.grpc:grpc-netty-shaded:1.45.0 (provided),
io.grpc:grpc-interop-testing:jar:1.45.1 / io.grpc:grpc-alts:1.45.1 (runtime) / io.grpc:grpc-netty-shaded:1.45.1 (compile),
com.google.cloud:google-cloud-core-grpc:jar:2.5.11 / com.google.api:gax-grpc:2.13.0 (compile) / io.grpc:grpc-netty-shaded:1.45.0 (runtime),
io.grpc:grpc-benchmarks:jar:1.45.1 / io.grpc:grpc-xds:1.45.1 (runtime) / io.grpc:grpc-netty-shaded:1.45.1 (compile),
io.grpc:grpc-netty-shaded:jar:1.45.1

The complaint on google-cloud-core-grpc having old GAX should be fixed by merging upcoming java-core release.