room-history: Replace ratio character with colon in timestamps

Apparently using the ratio character can create issues for RTL languages.

src/session/view/content/room_history/member_timestamp/row.rs

@@ -106,13 +106,13 @@ mod imp {
                 // For example, "May 5 at 01:20 PM".
                 // Do not change the time format as it will follow the system settings.
                 // See `man strftime` or the documentation of g_date_time_format for the available specifiers: <https://docs.gtk.org/glib/method.DateTime.format.html>
-                gettext("%B %-e at %I∶%M %p")
+                gettext("%B %-e at %I:%M %p")
             } else {
                 // Translators: this is a date and a time in 24h format.
                 // For example, "May 5 at 13:20".
                 // Do not change the time format as it will follow the system settings.
                 // See `man strftime` or the documentation of g_date_time_format for the available specifiers: <https://docs.gtk.org/glib/method.DateTime.format.html>
-                gettext("%B %-e at %H∶%M")
+                gettext("%B %-e at %H:%M")
             };
             let label = datetime.format(&format).unwrap();
 

src/session/view/content/room_history/message_row/mod.rs

@@ -236,7 +236,7 @@ mod imp {
 
             let clock_format = Application::default().system_settings().clock_format();
             let time = if clock_format == ClockFormat::TwelveHours {
-                datetime.format("%I∶%M %p").unwrap()
+                datetime.format("%I:%M %p").unwrap()
             } else {
                 datetime.format("%R").unwrap()
             };