fix: Sequence[Index] instead of Sequence

Author: cmp0xff

pandas-stubs/core/indexes/base.pyi

@@ -407,7 +407,7 @@ class Index(IndexOpsMixin[S1]):
     @overload
     def append(self, other: Index[S2]) -> Index[S1 | S2]: ...
     @overload
-    def append(self, other: Sequence) -> Index: ...
+    def append(self, other: Sequence[Index]) -> Index: ...
     def putmask(self, mask, value): ...
     def equals(self, other) -> bool: ...
     @final