[Keymap] Rework my Tsangan layout; turn off mousekeys (#8836)

* Give Tsangan layout a real Fn2 layer

* Disable mouse keys to work around qmk#8323

I don't actually use this feature, so there's no reason for it to be
enabled anyway, and it seems to cause spurious wakeups on Windows.

users/bcat/rules.mk

@@ -3,9 +3,8 @@ SRC += bcat.c
 # Enable Bootmagic Lite to consistently reset to bootloader and clear EEPROM.
 BOOTMAGIC_ENABLE = lite
 
-# Enable mouse and media keys on all keyboards.
+# Enable media keys on all keyboards.
 EXTRAKEY_ENABLE = yes
-MOUSEKEY_ENABLE = yes
 
 # Disable some unwanted features on all keyboards.
 API_SYSEX_ENABLE = no
@@ -13,6 +12,7 @@ COMMAND_ENABLE = no
 CONSOLE_ENABLE = no
 FAUXCLICKY_ENABLE = no
 MIDI_ENABLE = no
+MOUSEKEY_ENABLE = no
 NKRO_ENABLE = no
 SLEEP_LED_ENABLE = no
 UCIS_ENABLE = no