rubocops/shared/url_helper: tweak SourceForge handling #30915

Job	Run time
syntax	1m 20s
formula audit	4m 20s
cask audit	2m 58s
tap syntax	6m 38s
test default formula (Ubuntu 22.04)	1m 33s
tests (online)	5m 5s
test default formula (Ubuntu 20.04)	2m 50s
update-test (Ubuntu 22.04)	27s
tests (generic OS)	3m 4s
test default formula (macOS 13 x86_64)	3m 48s
vendored gems	43s
update-test (macOS)	38s
tests (Ubuntu 22.04)	3m 7s
test default formula (macOS 15 arm64)	1m 25s
tests (Ubuntu 20.04)	4m 6s
tests (macOS 13 x86_64)	8m 39s
tests (macOS 15 arm64)	5m 7s
	55m 48s

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