revert: "chore: Replace messageMixing with useMessage composable [CW-3475]" (#10011)

Reverts chatwoot/chatwoot#9942

This was causing the widget email input to break

app/javascript/widget/mixins/messageMixin.js

@@ -0,0 +1,13 @@
+export default {
+  computed: {
+    messageContentAttributes() {
+      const { content_attributes: attribute = {} } = this.message;
+      return attribute;
+    },
+    hasAttachments() {
+      return !!(
+        this.message.attachments && this.message.attachments.length > 0
+      );
+    },
+  },
+};