fix: prefer Referer header over Referrer

[bjohansebas]

Unlike #4106, which deprecates the use of referrer, this PR does the opposite, it prefers referer over referrer. According to RFC 9110, section 10.1.3, the specification technically already takes into account the use of referrer as well, so I think it’s fine to keep that validation. That said, we should still prefer reading the value from referer first.

The "Referer" [sic] header field allows the user agent to specify a URI reference for the resource from which the target URI was obtained (i.e., the "referrer", though the field name is misspelled). A user agent MUST NOT include the fragment and userinfo components of the URI reference [URI], if any, when generating the Referer field value

closes #4106 closes #3951