add module mapping for cloud-sql-python-connector (#20669)

Was trying to run tests using pants that imported
`google.cloud.sql.connector`, but ended up getting a module not found
error.

src/python/pants/backend/python/dependency_inference/default_module_mapping.py

@@ -112,6 +112,7 @@ def two_groups_hyphens_two_replacements_with_suffix(
     "beautifulsoup4": ("bs4",),
     "bitvector": ("BitVector",),
     "cattrs": ("cattr", "cattrs"),
+    "cloud-sql-python-connector": ("google.cloud.sql.connector",),
     "databricks-sdk": ("databricks.sdk",),
     "databricks-sql-connector": (
         "databricks.sql",