Update GC stage and shipping (#348)

See
https://bugzilla.mozilla.org/show_bug.cgi?id=1845373
and
https://groups.google.com/a/chromium.org/g/blink-dev/c/K_GpDF0y5Q8/m/XIJSfbTHBwAJ

features.json

@@ -24,7 +24,7 @@
 		"gc": {
 			"description": "Garbage collection",
 			"url":"https://github.com/WebAssembly/gc",
-			"phase": 3
+			"phase": 4
 		},
 		"jspi": {
 			"description": "JS Promise Integration",
@@ -101,7 +101,7 @@
 				"bulkMemory": "75",
 				"exceptions": "95",
 				"extendedConst": "114",
-				"gc": ["flag", "Requires flag `chrome://flags/#enable-webassembly-garbage-collection`"],
+				"gc": ["flag", "119"],
 				"jspi": ["flag", "Requires flag `chrome://flags/#enable-experimental-webassembly-stack-switching`"],
 				"memory64": ["flag", "Requires flag `chrome://flags/#enable-experimental-webassembly-features`"],
 				"multiMemory": ["flag", "Requires flag `chrome://flags/#enable-experimental-webassembly-features`"],
@@ -125,7 +125,7 @@
 				"bulkMemory": "79",
 				"exceptions": "100",
 				"extendedConst": "112",
-				"gc": [ "flag", "Can be enabled by setting the preference `javascript.options.wasm_gc` in `about:config`"],
+				"gc": [ "flag", "120"],
 				"memory64": ["flag", "Enabled in Nightly, unavailable in Beta/Release"],
 				"multiMemory": ["flag", "Enabled in Nightly, and behind preference flag javascript.options.wasm_multi_memory"],
 				"multiValue": "78",