bblayers: Remove meta-rust

Most of it was merged into openembedded-core [1].

[1] https://git.openembedded.org/openembedded-core/commit/?id=3ed57578cca93ff1ba4e0bf3f25566e10659a2f9

Author: danielbatw

conf/bblayers.conf

@@ -15,7 +15,6 @@ BBLAYERS = " \
   ${BSPDIR}/sources/meta-openembedded/meta-webserver \
   ${BSPDIR}/sources/meta-iot-cloud \
   ${BSPDIR}/sources/meta-qt5 \
-  ${BSPDIR}/sources/meta-rust \
   ${BSPDIR}/sources/meta-bytesatwork \
   ${BSPDIR}/sources/meta-freescale \
   ${BSPDIR}/sources/meta-bytesatwork-nxp \