chore: set release-please base version as 1.23.4 (#477)

We have release v1.23.4 on the main branch so release-please can use
that as the base version going forward.

Release-As: 1.23.5

.release-please-manifest.json

@@ -17,5 +17,5 @@
     }
   ],
   "extra-files": ["src/momento/__init__.py"],
-  ".": "1.23.3"
+  ".": "1.23.4"
 }