chore(internal/gapicgen): update microgen to v0.23.5 (#5181)

In REST clients, singular, primitive required fields will be added to query params regardless of if they are default empty value or not.

This is the fix for #5174 which will come in the next regen.

internal/gapicgen/cmd/genbot/Dockerfile

@@ -27,7 +27,7 @@ RUN go install github.com/golang/protobuf/protoc-gen-go@v1.5.2 && \
     go install golang.org/x/lint/golint@latest && \
     go install golang.org/x/tools/cmd/goimports@latest && \
     go install honnef.co/go/tools/cmd/staticcheck@latest && \
-    go install github.com/googleapis/gapic-generator-go/cmd/protoc-gen-go_gapic@v0.23.4
+    go install github.com/googleapis/gapic-generator-go/cmd/protoc-gen-go_gapic@v0.23.5
 ENV PATH="${PATH}:/root/go/bin"
 
 # Source: http://debuggable.com/posts/disable-strict-host-checking-for-git-clone:49896ff3-0ac0-4263-9703-1eae4834cda3