Fixes <https://bugs.gnu.org/36763>.
Previously, the logical and connecting the regexps did not output the expected
results (introduced in 8874faaaac).
* guix/ui.scm (relevance)
[score]: Change its arguments.
[regexp->score]: New procedure.
* tests/ui.scm ("package-relevance"): Add test.
Signed-off-by: Ludovic Courtès <ludo@gnu.org>