Expect upper-case hex digits in escaped redirect URL

[gammazero]

This is needed for ipfs/boxo#779.

Regardless of boxo changes it seems more correct to expect upper-case hex for percent-escaped characters:

RFC3986 §2.1

For consistency, URI producers and normalizers should use uppercase hexadecimal digits for all percent-encodings.

[github-actions]

Results against Kubo master:
(check the action's summary for the full results)

Summary

Tests	Failures	Errors	Skipped
1308	6	0	0

[github-actions]

Results against Kubo latest:
(check the action's summary for the full results)

Summary

Tests	Failures	Errors	Skipped
1308	6	0	0