chore(internal/librariangen): update gapic-generator-go to v0.54.0 (googleapis#13060)

Author: jskeet

internal/librariangen/Dockerfile

@@ -64,7 +64,7 @@ ENV PROTOC_VERSION=25.7
 ENV GO_PROTOC_PLUGIN_V1_VERSION=1.5.4
 ENV GO_PROTOC_PLUGIN_V2_VERSION=1.35.2
 ENV GO_GRPC_PLUGIN_VERSION=1.3.0
-ENV GAPIC_GENERATOR_VERSION=0.53.1
+ENV GAPIC_GENERATOR_VERSION=0.54.0
 ENV STATICCHECK_VERSION=2023.1.6
 
 # Set up a home directory for the non-root user that will be running this container.