notation-incompatible-format warnings

There is a bunch of warnings like this one:
```
COQC solutions/SsrStyle_solutions.v
File "./solutions/SsrStyle_solutions.v", line 1, characters 0-65:
Warning: Notation "[ rel _ _ : _ | _ ]" was already defined with a different
format in scope fun_scope. [notation-incompatible-format,parsing]
```

Looks like for Coq 8.12 there is no other solution but disable this warning.