[lldb] Fix bad method call in TestExprDiagnostics.py

Fixes

    Traceback (most recent call last):
      File "/home/buildbot/worker/as-builder-9/lldb-remote-linux-ubuntu/llvm-project/lldb/packages/Python/lldbsuite/test/lldbtest.py", line 1770, in test_method
        return attrvalue(self)
               ^^^^^^^^^^^^^^^
      File "/home/buildbot/worker/as-builder-9/lldb-remote-linux-ubuntu/llvm-project/lldb/test/API/commands/expression/diagnostics/TestExprDiagnostics.py", line 255, in test_command_expr_sbdata
        self.assertEquals(error.GetType(), lldb.eErrorTypeExpression)
        ^^^^^^^^^^^^^^^^^
    AttributeError: 'ExprDiagnosticsTestCase' object has no attribute 'assertEquals'. Did you mean: 'assertEqual'?

`assertEqual` is a method inherited from `unittest.TestCase`.

See llvm#120784 and llvm#120784 (comment)

Author: carlocab

lldb/test/API/commands/expression/diagnostics/TestExprDiagnostics.py

@@ -252,7 +252,7 @@ def check_error(diags):
         value = frame.EvaluateExpression("a+b")
         error = value.GetError()
         self.assertTrue(error.Fail())
-        self.assertEquals(error.GetType(), lldb.eErrorTypeExpression)
+        self.assertEqual(error.GetType(), lldb.eErrorTypeExpression)
         data = error.GetErrorData()
         version = data.GetValueForKey("version")
         self.assertEqual(version.GetIntegerValue(), 1)