Rewrite a fake language code "tl" in SpellChecker.

With following CLs, we already have a special rewrite rule of "tl" to
"fil" for IMEs that are targeting older versions of Android earlier than
Lollipop that did not support three letter language codes and used
"tl" (Tagalog) as the language string for "fil" (Filipino).
  - 92280cd3 [1]
  - ed65bc0c [2]

  [1]: I94f203bddceb9c87710cb187cc3cc0ee6d9092a5
  [2]: Ica9cd2baac002c406f92331aadd7725d7424046a

With this CL, we have the same rewrite rule for spell checker services.

Bug: 20696126
Change-Id: I0af0f520a15337e33973391c9965364e3ae1ee4c