Remove unneeded pseudo_id check.

It's already in a block with if (pseudo_id == kPseudoIdFirstLetter).

Just a nit I noticed while seeing the patch for issue 853551.

Bug: 853551
Change-Id: Ib4fadc46497c2ed4142f88f9d57938273acf622d
Reviewed-on: https://chromium-review.googlesource.com/1105831Reviewed-by: Rune Lillesveen <futhark@chromium.org>
Commit-Queue: Emilio Cobos Álvarez <emilio@chromium.org>
Cr-Commit-Position: refs/heads/master@{#568415}

third_party/blink/renderer/core/dom/element.cc

@@ -2402,7 +2402,7 @@ void Element::RebuildPseudoElementLayoutTree(
     // ::first-letter.
     if (!element)
       element = CreatePseudoElementIfNeeded(pseudo_id);
-    else if (pseudo_id == kPseudoIdFirstLetter && UpdateFirstLetter(element))
+    else if (UpdateFirstLetter(element))
       return;
   }
   if (element && element->NeedsRebuildLayoutTree(whitespace_attacher))