[REG] DIP1000 scope array of arrays comparison results in weird error

Works as of 2.111, fails on master:

```D
// REQUIRED_ARGS: -preview=dip1000
void assertEq(scope int[][3] x) @safe
{
	bool b = x == x;
}
```

Expected to pass, but it errors:
```
app.d(4): Error: can't infer return type in function `assertEq`
    bool b = x == x;
```

Introduced by https://github.com/dlang/dmd/pull/21513