[LLDB] Fix typo in TestDataFormatterSynthVal.py

This is follow up to 039b28e to fix a typo to make sure skipped
part of test is only skipped for AArch64 Windows platform.

Author: omjavaid

lldb/test/API/functionalities/data-formatter/data-formatter-synthval/TestDataFormatterSynthVal.py

@@ -96,7 +96,7 @@ def cleanup():
 
         # check that an aptly defined synthetic provider does not affect
         # one-lining
-        if self.isAArch64Windows():
+        if not self.isAArch64Windows():
             self.expect(
                 "expression struct Struct { myInt theInt{12}; }; Struct()",
                 substrs=['(theInt = 12)'])