utils,playertoolbar: Use regular colon as time divider

The GNOME HIG suggests using an alternate character for the hour,
minutes divider (Teams/Design/hig-www#127). This leads to reversed time
ordering in RTL languages.

Use „:” (U+003A) again instead of „∶” (U+2236) for now. This will fix
the reversed time in RTL languages.

Fixes: #509