PY-86002 Adjust PyUnnecessaryCastInspectionTest.test okay expected result

`UnsafeUnion[int | str]` is considered a subtype of `str`, so the cast is redundant.


(cherry picked from commit 550a9d55715564492169175c5e20cfbf1ade4b20)

IJ-MR-184619

GitOrigin-RevId: 854131d04308bd97b12ef06cc10a4aa89238c9ef

python/testSrc/com/jetbrains/python/inspections/PyUnnecessaryCastInspectionTest.kt

@@ -52,7 +52,7 @@ from typing import cast
         cast(B, C())  # ok
         
         a: int | str
-        b = cast(str, a)  # ok
+        b = <weak_warning descr="Unnecessary cast; type is already 'str'">cast(str,</weak_warning> a)  # ok
       """.trimIndent()
     )
   }