Vent sussy NBSP from test case

[KotlinIsland]

This fixes a test case, the test case included a sussy NBSP which resulted in the test being completely invalid.

I have now updated the testcase to vent the impostor and expect the correct result instead.

With nbsp:
x.trifdsgdfgm() # E: AMONGUS [attr-defined]

> pytest -n0 -k testEnableDifferentErrorCode
...
1 passed

with space:
x.trifdsgdfgm() # E: AMONGUS [attr-defined]

> pytest -n0 -k testEnableDifferentErrorCode
...

_____________________________________________________________________________________________________ testEnableDifferentErrorCode _____________________________________________________________________________________________________
data: /home/amongus/projects/mypy/test-data/unit/check-flags.test:1991:
/home/amongus/projects/mypy/mypy/test/testcheck.py:140: in run_case
    self.run_case_once(testcase)
/home/amongus/projects/mypy/mypy/test/testcheck.py:227: in run_case_once
    assert_string_arrays_equal(output, a, msg.format(testcase.file, testcase.line))
E   AssertionError: Unexpected type checker output (/home/amongus/projects/mypy/test-data/unit/check-flags.test, line 1991)
--------------------------------------------------------------------------------------------------------- Captured stderr call ---------------------------------------------------------------------------------------------------------
Expected:
  main:3: error: AMONGUS [attr-defined]         (diff)
Actual:
  (empty)

======================================================================================================= short test summary info ========================================================================================================
FAILED mypy/test/testcheck.py::TypeCheckSuite::check-flags.test::testEnableDifferentErrorCode

[github-actions]

According to mypy_primer, this change has no effect on the checked open source code. 🤖🎉