terminal-app: remove -Wdiscarded-qualifiers warnings

[rbuj]

terminal-app.c:152:26: warning: passing argument 2 of ‘terminal_app_profile_list_notify_cb’ discards ‘const’ qualifier from pointer target type [-Wdiscarded-qualifiers]
terminal-app.c:153:29: warning: passing argument 2 of ‘terminal_app_default_profile_notify_cb’ discards ‘const’ qualifier from pointer target type [-Wdiscarded-qualifiers]
terminal-app.c:155:27: warning: passing argument 2 of ‘terminal_app_encoding_list_notify_cb’ discards ‘const’ qualifier from pointer target type [-Wdiscarded-qualifiers]
terminal-app.c:143:28: warning: passing argument 2 of ‘terminal_app_system_font_notify_cb’ discards ‘const’ qualifier from pointer target type [-Wdiscarded-qualifiers]
terminal-app.c:149:35: warning: passing argument 2 of ‘terminal_app_enable_menu_accels_notify_cb’ discards ‘const’ qualifier from pointer target type [-Wdiscarded-qualifiers]
terminal-app.c:146:30: warning: passing argument 2 of ‘terminal_app_enable_mnemonics_notify_cb’ discards ‘const’ qualifier from pointer target type [-Wdiscarded-qualifiers]

[raveit65]

@rbuj How do you get this warnings? Adding -Wdiscarded-qualifiers as CFLAG doesn#t give me those warnings.

[raveit65]

Damned, found it for myself https://github.com/mate-desktop/engrampa/pull/302#issuecomment-529098261 It's WARN_CFLAGS="-Wwrite-strings" for some reasons.