Remove unnecessary `android:"path"` tags in rust

Custom_bindgen is handled by adding a relevant dependency tag.
Flags and Ld_flags are not paths/references to other modules.

Test: go test soong tests
Change-Id: Ic6a69521102318b3b9f29b59560bcefbc9aff8fa
diff --git a/rust/bindgen.go b/rust/bindgen.go
index bcc26b8..9198e6d 100644
--- a/rust/bindgen.go
+++ b/rust/bindgen.go
@@ -79,7 +79,7 @@
 	// binary must expect arguments in a similar fashion to bindgen, e.g.
 	//
 	// "my_bindgen [flags] wrapper_header.h -o [output_path] -- [clang flags]"
-	Custom_bindgen string `android:"path"`
+	Custom_bindgen string
 }
 
 type bindgenDecorator struct {