doc: remove non-existing command swd wcr

doc: remove non-existing command swd wcr

The commands has been dropped in commit 150b7d26f213 ("arm_adi_v5:
Update DP (Debug Port) registers defined in ADIv5.2.") but the
documentation still keeps it.

Remove it!

Change-Id: I4e88f481d943f064d919f8065562052244122bf0
Signed-off-by: Antonio Borneo <borneo.antonio@gmail.com>
Fixes: 150b7d26f213 ("arm_adi_v5: Update DP (Debug Port) registers defined in ADIv5.2.")
Reviewed-on: https://review.openocd.org/c/openocd/+/6722
Tested-by: jenkins
Reviewed-by: Tomas Vanek <vanekt@fbl.cz>