rust: Remove rust_ffi_rlibs, keep rust_ffi_static

rust_ffi_static and rust_ffi_rlibs both alias to rust_library_rlib now.
We need to think about whether we need these aliases at all.

There are no users of rust_ffi_rlibs at the moment as developers are
continuing to declare rust_ffi_static modules. Let's remove this alias
in the meantime at least to simplify things.

Bug: 350633786
Bug: 383552450
Test: m blueprint_tests && m rust
Change-Id: I6be895ddbffc5ac6303f2edc9ab20f7c20cd1591
diff --git a/rust/rust_test.go b/rust/rust_test.go
index 7e64c0a..90c1f61 100644
--- a/rust/rust_test.go
+++ b/rust/rust_test.go
@@ -434,21 +434,21 @@
 
 func TestRustRlibs(t *testing.T) {
 	ctx := testRust(t, `
-		rust_ffi_rlib {
+		rust_ffi_static {
 			name: "libbar",
 			crate_name: "bar",
 			srcs: ["src/lib.rs"],
 			export_include_dirs: ["bar_includes"]
 		}
 
-		rust_ffi_rlib {
+		rust_ffi_static {
 			name: "libfoo",
 			crate_name: "foo",
 			srcs: ["src/lib.rs"],
 			export_include_dirs: ["foo_includes"]
 		}
 
-		rust_ffi_rlib {
+		rust_ffi_static {
 			name: "libbuzz",
 			crate_name: "buzz",
 			srcs: ["src/lib.rs"],