fix: Make IS_MAYBE_MIRAGE work in Firefox

[MichalBryxi]

Description

• FF vs Chrome produces different toString() for native window.fetch.
• This patch fixes that.

Firefox

"function fetch() {
    [native code]
}"

Chrome

'function fetch() { [native code] }'

Notes for the release

Fix of a bug where Mirage identification failed for Firefox.

[MichalBryxi]

One smarter person than me suggested that maybe a better option would be to make the toString() whitespace agnostic and thus avoid any formatting issues whatsoever:

window.fetch.toString().replace(/\s+/g, '') !== 'function fetch() { [native code] }'.replace(/\s+/g, '');

[runspired]

@MichalBryxi yeah I thought of that too, am down. Runs in debug only though so not a huge thing either way