submodules: delete CMSIS_5 from the repository

See raspberrypi/pico-setup#57

Clones of debugprobe or invocations of pico-setup.sh frequently
encounter errors relating to bandwidth budgets. These sporadic errors
are due to the large size of the CMSIS_5 repo clone exhausting the
bandwidth quotas on Github, so drop this in favour of a downstream copy
of the relevant CMSIS-DAP firmware files.

Users are advised to delete and regenerate the build directory.

Optionally, reclaim filesystem space by removing .git/modules/CMSIS_5
and all subdirectories.

Author: P33M

.gitmodules

@@ -1,6 +1,3 @@
-[submodule "CMSIS_5"]
-	path = CMSIS_5
-	url = https://github.com/ARM-software/CMSIS_5
 [submodule "freertos"]
 	path = freertos
 	url = https://github.com/FreeRTOS/FreeRTOS-Kernel