config/profile.fish.in: Prevent bracketed variables and unmatched wildcard errors

config/profile.fish.in: Prevent bracketed variables and unmatched wildcard errors

Fish does not support bracketed variables in scripts.  Remove brackets
from the variable ${prefix} in profile.fish before installation to
prevent this error.

Fish also raises an error for unmatched wildcards, except for special
cases like the set command.  Use a wildcard to match .urls files using
the set command instead of cat to prevent an unmatched wildcard error
when no .urls files are found.

Signed-off-by: Aaron Merey <amerey@redhat.com>