[BUGFIX lts] Avoid console.trace for every Ember.warn

Originally (Ember < 3.2), `Ember.warn` used `Ember.Logger` as an
abstraction layer in case `console` was not present. Since
`Ember.Logger` was deprecated in
[emberjs/rfcs#297](https://emberjs.github.io/rfcs/0297-deprecate-ember-logger.html)
the internals have been refactored to use `console` directly instead.

When that change was made, the following:

```js
    Logger.warn(`WARNING: ${message}`);
    if ('trace' in Logger) {
      Logger.trace();
    }
```

Was changed to:

```js
    console.warn(`WARNING: ${message}`);
    if (console.trace) {
      console.trace();
    }
```

This _seems_ correct, however when you dig into it you will notice that
the `Ember.Logger` class **never** had a `.trace` method! The reason for
the original `'trace' in Logger` check was specifically so that you
_could_ do `Ember.Logger.trace = () => console.trace` _IIF_ you wanted
to see where a given warning was coming from. That was added back in
2012, but since then the developer tools of modern browsers have gotten
massively better. At this point, **every** `console.log`/`console.warn`
tracks its stack trace so that you can drill into the source in the dev
tools. The primary difference between that functionality and calling
`console.trace()` directly like this is that with `console.warn`
the stack trace is hidden by default (and has to be manually expanded),
whereas with `console.trace()` it is _always_ called and the full stack
is printed.

Ultimately, this means that when we refactored to address the
`Ember.Logger` deprecation, we began calling `console.trace` for _every_
`Ember.warn` invocation and the `console.trace()` calls make the console
fairly unusable even with a very low volumn of warnings.

(cherry picked from commit 3e45eb9)

packages/@ember/debug/lib/warn.ts

@@ -58,9 +58,6 @@ if (DEBUG) {
   registerHandler(function logWarning(message) {
     /* eslint-disable no-console */
     console.warn(`WARNING: ${message}`);
-    if (console.trace) {
-      console.trace();
-    }
     /* eslint-enable no-console */
   });