dts: librem5: Remove broken-cd from mmc1 definition

Card Detect was broken on Aspen, but has been fixed on Birch onward,
and we don't support Aspen with this device tree anyway.
2 jobs for broken-cd in 46 minutes and 4 seconds (queued for 2 seconds)
latest
Status Job ID Name Coverage
  Build
passed #260889
librem5
build:aarch64

00:13:21

passed #260890
librem5:arm64
build:deb

00:46:04