Remove rust submodule

Signed-off-by: Marc Duiker <marcduiker@users.noreply.github.com>

Author: marcduiker

.gitmodules

@@ -20,6 +20,3 @@
 [submodule "sdkdocs/pluggable-components/go"]
 	path = sdkdocs/pluggable-components/go
 	url = https://github.com/dapr-sandbox/components-go-sdk
-[submodule "sdkdocs/rust"]
-	path = sdkdocs/rust
-	url = https://github.com/dapr/rust-sdk.git