Restore stubtest 0.930 (#6663)

stdlib/stringprep.pyi

@@ -1,3 +1,11 @@
+b1_set: set[int]
+b3_exceptions: dict[int, str]
+c22_specials: set[int]
+c6_set: set[int]
+c7_set: set[int]
+c8_set: set[int]
+c9_set: set[int]
+
 def in_table_a1(code: str) -> bool: ...
 def in_table_b1(code: str) -> bool: ...
 def map_table_b3(code: str) -> str: ...