[fix] warning on reactive use of module const (#6606) (#6607)

src/compiler/compile/Component.ts

@@ -1312,7 +1312,7 @@ export default class Component {
 
 								if (variable) {
 									variable.is_reactive_dependency = true;
-									if (variable.module) {
+									if (variable.module && variable.writable) {
 										should_add_as_dependency = false;
 										module_dependencies.add(name);
 									}

test/validator/samples/reactive-module-const-variable/input.svelte

@@ -0,0 +1,9 @@
+<script context="module">
+	export const foo = 123;
+	export const doFoo = (foo) => foo;
+</script>
+
+<script>
+	$: bar = foo;
+	$: doFoo(bar);
+</script>

test/validator/samples/reactive-module-const-variable/warnings.json

@@ -0,0 +1,2 @@
+[
+]