These type checks were overlapping with `assignOperatorWithWrongType` is
are no longer needed now that `assignOperatorWithWrongType` is improved.
They were causing FPs and misleading error messages on uninstantiated
templates.
Without the last commit, this addition to the test gives the following
results:
```
+| AV Rule 82.cpp:176:14:176:22 | operator= | Assignment operator in class Forgivable does not return a reference to *this. |
+| AV Rule 82.cpp:181:14:181:22 | operator= | Assignment operator in class Forgivable does not return a reference to *this. |
```
