Remove mozc from whitelist.

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 66 matching lines @@
 xkb:ca::fra     ca      fr      
 xkb:ch:fr:fra   ch(fr)  fr      
 
 # German
 xkb:de::ger     de      de      
 xkb:de:neo:ger  de(neo) de      
 xkb:be::ger     be      de      
 xkb:ch::ger     ch      de      
 
 # Japanese
-mozc    us      ja
-mozc-jp jp      ja      
-mozc-dv us(dvorak)      ja      
 # |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      
 
 # Thai
 m17n:th:kesmanee        us      th
@@ skipping 104 matching lines @@
 xkb:pt::por     pt      pt-PT   
 xkb:ro::rum     ro      ro      
 xkb:se::swe     se      sv      
 xkb:sk::slo     sk      sk      
 xkb:si::slv     si      sl      
 xkb:rs::srp     rs      sr      
 xkb:tr::tur     tr      tr      
 xkb:ua::ukr     ua      uk      
 # TODO(yusukes): Support xkb:latam:deadtilde:spa and/or xkb:latam:nodeadkeys:spa
 # if necessary.