default-apps: switch away from deprecated function

cc-default-apps-panel.c:101 uses g_pattern_match_string, which is now considered deprecated in Glib. It is better to use the 2.70+ g_pattern_spec_match_string, which works as a drop-in replacement. This helps with function organization, as the original was created as a general Glib function while g_pattern_spec_match_string works under the PatternSpec module.

This patch swaps the usage to the newer function, creating no functional difference and resolving a deprecated functions warning.