LibWeb+WebContent: Do not include DOM HTML in text test expectations

For example, in the following abbreviated test HTML:

    <span>some text</span>
    <script>println("whf")</script>

We would have to craft the expectation file to include the "some text"
segment, usually with some leading whitespace. This is a bit annoying,
and makes it difficult to manually craft expectation files.

So instead of comparing the expectation against the entire DOM inner
text, we now send the inner text of just the <pre> element containing
the test output when we invoke `internals.signalTextTestIsDone`.

Tests/LibWeb/Text/expected/WebAnimations/animation-methods/cancel.txt

@@ -1,4 +1,4 @@
-   Calling cancel() aborts the ready promise with an error of type AbortError: true
+Calling cancel() aborts the ready promise with an error of type AbortError: true
 Calling cancel() aborts the finished promise with an error of type AbortError: true
 Calling cancel() recreates the ready promise: true
 Calling cancel() recreates the finished promise: true

Tests/LibWeb/Text/expected/WebAnimations/animation-methods/finish.txt

@@ -1,4 +1,4 @@
-   Cannot finish an animation with no effective playback rate
+Cannot finish an animation with no effective playback rate
 Cannot finish an animation with an infinite effect end
 finish() updates animation's pending playback rate
 finish() updates currentTime of animation with positive playback rate

Tests/LibWeb/Text/expected/WebAnimations/animation-methods/pause.txt

@@ -1,4 +1,4 @@
-   Cannot pause a reversing idle animation with infinite effect end
+Cannot pause a reversing idle animation with infinite effect end
 Calling pause() does not synchronously update pending playback rate
 Calling pause() does not synchronously resolve animation's ready promise
 Calling pause() does not send any events

Tests/LibWeb/Text/expected/WebAnimations/animation-methods/persist.txt

@@ -1,4 +1,4 @@
-   persist() sets animation's replaceState to persist
+persist() sets animation's replaceState to persist
 persist() undoes the Document removal effects: true
 Animations are properly replaced when covered by another animation
 persist() keeps an animation from being replaced

Tests/LibWeb/Text/expected/WebAnimations/animation-methods/play.txt

@@ -1,4 +1,4 @@
-   Cannot rewind an animation with an infinite effect end
+Cannot rewind an animation with an infinite effect end
 play() leaves animation's startTime unresolved: true
 play() does not recreate the animation's ready promise
 play() does not synchronously resolve the ready promise

Tests/LibWeb/Text/expected/WebAnimations/animation-methods/reverse.txt

@@ -1,4 +1,4 @@
-   reverse() does not update the playback rate synchronously
+reverse() does not update the playback rate synchronously
 reverse() updates the playback rate asynchronously
 Cannot reverse an animation with an infinite effect end
 reverse() does not update the playback rate if calling play() would throw an exception

Tests/LibWeb/Text/expected/WebAnimations/animation-methods/updatePlaybackRate.txt

@@ -1,4 +1,4 @@
-   updatePlaybackRate() updates an idle animation's playback rate immediately
+updatePlaybackRate() updates an idle animation's playback rate immediately
 updatePlaybackRate() updates a running animation's playback rate after an animation frame
 updatePlaybackRate() updates a paused animation's playback rate after an animation frame
 updatePlaybackRate() updates a finished animation's playback rate after an animation frame