[xDS Interop] Add v1.61.0 release of grpc-go to interop matrix (#35647)

<!--

If you know who should review your pull request, please assign it to that
person, otherwise the pull request would get assigned randomly.

If your pull request is for a specific language, please add the appropriate
lang label.

-->

Closes #35647

COPYBARA_INTEGRATE_REVIEW=https://github.com/grpc/grpc/pull/35647 from zasweq:go-releasee 419db97b9b
PiperOrigin-RevId: 602821918

tools/interop_matrix/client_matrix.py

@@ -294,6 +294,7 @@ LANG_RELEASE_MATRIX = {
             ("v1.58.3", ReleaseInfo(runtimes=["go1.19"])),
             ("v1.59.0", ReleaseInfo(runtimes=["go1.19"])),
             ("v1.60.1", ReleaseInfo(runtimes=["go1.19"])),
+            ("v1.61.0", ReleaseInfo(runtimes=["go1.19"])),
         ]
     ),
     "java": OrderedDict(