match: simplify the rust-side file pattern kind parsing There's no need to add the ':' characters if we're simply pattern matching against constants next.

pager.pager=p0 # $TESTTMP/sysrc:4
ui.editor=e1 # $TESTTMP/userrc:2

pager.pager=p2 # $PAGER
ui.editor=e1 # $TESTTMP/userrc:2