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.
Adding this call to `getUnspecifiedType` makes the error message better
in the presence of typedefs and qualifiers on an assignment operator
return type. It's also needed to avoid losing valid results in the
commit that comes after this.
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. |
```
