refactor: fix phpstan errors in `URI` and `SiteURI` #13139

Job	Run time
Setup PHP Version for Code Coverage	2s
Others (8.1) / Sanity Tests	2m 7s
Others (8.2) / Sanity Tests	1m 56s
Others (8.3) / Sanity Tests	2m 6s
Others (8.4) / Sanity Tests	1m 55s
DatabaseLive	0s
CacheLive	0s
Upload coverage results to Coveralls	0s
SeparateProcess	0s
	8m 6s

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