remove git meta-lts-mixins for rust

not necessary

Author: thomas-roos

.gitmodules

@@ -106,10 +106,6 @@
 	path = layers/sw/meta-clang
 	url = https://github.com/kraj/meta-clang.git
 	branch = scarthgap
-[submodule "layers/sw/meta-lts-mixins"]
-	path = layers/sw/meta-lts-mixins
-	url = https://git.yoctoproject.org/meta-lts-mixins
-	branch = scarthgap/rust
 [submodule "layers/sw/meta-browser"]
 	path = layers/sw/meta-browser
 	url = https://github.com/OSSystems/meta-browser.git