Add stub for datetime.time.fromisoformat introduced in 3.7 (#2426)

stdlib/2and3/datetime.pyi

@@ -106,6 +106,9 @@ class time:
     def __gt__(self, other: time) -> bool: ...
     def __hash__(self) -> int: ...
     def isoformat(self) -> str: ...
+    if sys.version_info >= (3, 7):
+        @classmethod
+        def fromisoformat(cls, time_string: str) -> time: ...
     def strftime(self, fmt: _Text) -> str: ...
     if sys.version_info >= (3,):
         def __format__(self, fmt: str) -> str: ...