Drop Python 3.8 branches (#13776)

stdlib/time.pyi

@@ -31,7 +31,7 @@ if sys.platform == "darwin":
         CLOCK_UPTIME_RAW_APPROX: int
         CLOCK_MONOTONIC_RAW_APPROX: int
 
-if sys.version_info >= (3, 9) and sys.platform == "linux":
+if sys.platform == "linux":
     CLOCK_TAI: int
 
 # Constructor takes an iterable of any type, of length between 9 and 11 elements.