rerere: wrap paths in output in sq

rerere: wrap paths in output in sq

It looks like most paths in the output in the git codebase are wrapped
in single quotes.  Standardize on that in rerere as well.

Apart from being more consistent, this also makes some of the strings
match strings that are already translated in other parts of the
codebase, thus reducing the work for translators, when the strings are
marked for translation in a subsequent commit.

Signed-off-by: Thomas Gummerer <redacted>
Signed-off-by: Junio C Hamano <redacted>