bug: Protoc --version dropped major version.

eg. 3.27.1 --> 27.1

setup.py

@@ -42,11 +42,11 @@ def _find_protoc() -> str | None:
     def _get_protoc_version(protoc: str) -> tuple[int, int, int]:
         protoc_version_string = str(subprocess.check_output([protoc, "--version"]))
         version_search = re.search(
-            r"((?P<major>(0|[1-9]\d*))\.(?P<minor>(0|[1-9]\d*))\.(?P<patch>(0|[1-9]\d*)))",
+            r"(((?P<major>(0|[1-9]\d*))\.)?(?P<minor>(0|[1-9]\d*))\.(?P<patch>(0|[1-9]\d*)))",
             protoc_version_string,
         )
 
-        return tuple(int(version_search.group(g)) for g in ("major", "minor", "patch"))  # type: ignore
+        return tuple(int(version_search.group(g)) if version_search.group(g) is not None else 3 for g in ("major", "minor", "patch"))  # type: ignore
 
     _executable: str | None
     _version: tuple[int, int, int] | None
@@ -113,10 +113,7 @@ def make_protobuf_requirement(major: int, minor: int, patch: int) -> str:
 
     # This encodes on which minor protobuf version the major python protobuf
     # version was bumped
-    protobuf_version_mapping = (
-        (3, 0),
-        (4, 21),
-    )
+    protobuf_version_mapping = ((3, 0), (4, 21), (5, 26))
 
     # We must subtract one because bisect gives the insertion point after...
     py_major = protobuf_version_mapping[