[IMP] runtime: simplify info message when running in dev mode

The owl dev info message may be useful, but does not bring that much
value. Also, this is even slightly annoying while debugging odoo, since
it is common to have to go to dev mode, and the message takes some
visual space, which is a distraction.  In this commit, we simplify it to
just warn that owl is in dev mode.

tests/components/props_validation.test.ts

@@ -1,6 +1,6 @@
 import { makeTestFixture, nextAppError, nextTick, snapshotEverything } from "../helpers";
 import { Component, onError, xml, mount, OwlError, useState } from "../../src";
-import { App, DEV_MSG } from "../../src/runtime/app";
+import { App } from "../../src/runtime/app";
 import { validateProps } from "../../src/runtime/template_helpers";
 import { Schema } from "../../src/runtime/validation";
 
@@ -13,7 +13,7 @@ let mockConsoleWarn: any;
 
 beforeAll(() => {
   console.info = (message: any) => {
-    if (message === DEV_MSG()) {
+    if (message === `Owl is running in 'dev' mode.`) {
       return;
     }
     info(message);