Instead of doing heterogeneous comparison at comptime. This makes the
following test pass (as it already does for stage1):

```zig
test {
    const x: f64 = 12.34;
    expect(x == 12.34);
}
```

There is already behavior test coverage for this, however, other bugs in
`std.fmt.parseFloat` are masking the failures.

From a language specification perspective, this makes sense because it
makes comptime comparisons with comptime_float work the same way they
work with runtime comparisons.