PEP 635: Minor typo fix in code sample (#3871)

Looks like an unclosed f-string.

peps/pep-0635.rst

@@ -1118,7 +1118,7 @@ be emulated by a user-defined class as follows::
 The proposal was to combine patterns with type annotations::
 
   match x:
-      case [a: int, b: str]: print(f"An int {a} and a string {b}:)
+      case [a: int, b: str]: print(f"An int {a} and a string {b}:")
       case [a: int, b: int, c: int]: print("Three ints", a, b, c)
       ...