PY-58374 Fix dict keys completion when editing an existing key

GitOrigin-RevId: 41434300f6ea0f776a115a869fb9578a84015471

python/testData/completion/dictLiteralCompletion/EditingKeyWithExistingValue/main.py

@@ -0,0 +1,10 @@
+from typing import TypedDict
+
+
+class Point(TypedDict):
+    coordinateX: int
+    coordinateY: int
+    coordinateZ: int
+
+
+p: Point = {'coo<caret>': 42, 'coordinateY': 42}