Don't pass -Z unstable-options to rustc; it's not needed for --includ…

…e-ignored anymore

Since rust-lang/rust#80053 this is in the
normal compiler, not only in the nightly one.

Part-of: <https://gitlab.gnome.org/GNOME/librsvg/-/merge_requests/856>

Makefile.am

@@ -191,7 +191,7 @@ check-local:
 	CARGO_TARGET_DIR=$(CARGO_TARGET_DIR)			\
 	LIBRSVG_BUILD_DIR=$(LIBRSVG_BUILD_DIR)			\
 	TESTS_OUTPUT_DIR=$(LIBRSVG_BUILD_DIR)/tests/output	\
-	$(CARGO) --locked test $(CARGO_VERBOSE) $(CARGO_TARGET_ARGS) $(CARGO_RELEASE_ARGS) --workspace -- --include-ignored -Z unstable-options
+	$(CARGO) --locked test $(CARGO_VERBOSE) $(CARGO_TARGET_ARGS) $(CARGO_RELEASE_ARGS) --workspace -- --include-ignored
 
 clean-local:
 	cd $(top_srcdir) &&			\