Removes m17n:vi:vni as the chromeos-keyboards has replaced it.

chromeos/ime/input_methods.txt

 # The list of input methods that we support. The input methods metadata is
 # also defined here. We use this data for the following purposes.
 #
 # 1. Exclude unnecessary input methods. For example, we don't need
 #    "ja:anthy", and "zh:pinyin" engines in ibus-m17n since we have better
 #    alternatives outside of ibus-m17n. Excluding these input methods from
 #    the IBus engine XML files, such as /usr/share/ibus/component/m17n.xml,
 #    makes the startup time of the IBus daemon faster. This filtering is
 #    done using a python script at build time of ibus-m17n.
 #    See crosbug.com/4161 for details.
@@ skipping 84 matching lines @@
 
 # Japanese
 # |kMozcJaInputMethodIds| in ibus_ui_controller.cc should also be updated when
 # a new Mozc Japanese IME for another keyboard layout is added.
 xkb:jp::jpn     jp      ja
 
 # Russian
 xkb:ru::rus     ru      ru
 xkb:ru:phonetic:rus     ru(phonetic)    ru
 
-# Vietnamese
-m17n:vi:vni     us      vi
-# Note: Since Chrome does not support "get surrounding text" feature yet,
-# Vietnames input methods, except 4 input methods above, in m17n-db should
-# not work fine. The 4 input methods in m17n-db (>= 1.6.0) don't require the
-# feature.
-
 # Keyboard layouts.
 xkb:br::por     br      pt-BR
 xkb:bg::bul     bg      bg
 xkb:bg:phonetic:bul     bg(phonetic)    bg
 xkb:ca:eng:eng  ca(eng) en-CA
 xkb:cz::cze     cz      cs
 xkb:cz:qwerty:cze       cz(qwerty)      cs
 xkb:ee::est     ee      et
 xkb:es::spa     es      es
 xkb:es:cat:cat  es(cat) ca
@@ skipping 19 matching lines @@
 xkb:si::slv     si      sl
 xkb:rs::srp     rs      sr
 xkb:tr::tur     tr      tr
 xkb:ua::ukr     ua      uk
 xkb:by::bel     by      be
 xkb:am:phonetic:arm     am      hy
 xkb:ge::geo     ge      ka
 xkb:mn::mon     mn      mn
 # TODO(yusukes): Support xkb:latam:deadtilde:spa and/or xkb:latam:nodeadkeys:spa
 # if necessary.