toNormalizeUrl should also ensure lowercase for the scheme

[Mugurell]

From https://www.rfc-editor.org/rfc/rfc3986#section-3.1

Although schemes are case-
insensitive, the canonical form is lowercase and documents that
specify schemes must do so with lowercase letters.  An implementation
should accept uppercase letters as equivalent to lowercase in scheme
names (e.g., allow "HTTP" as well as "http") for the sake of
robustness but should only produce lowercase scheme names for
consistency.

This would also help fix mozilla-mobile/fenix#24692

┆Issue is synchronized with this Jira Task

[jknair0]

I am interested to pick this up!

[csadilek]

Fixed by #12001.