Remove unused MJPEG define from libjpeg-turbo GN and GYP

DEPS

 # This file is used to manage the dependencies of the Chromium src repo. It is
 # used by gclient to determine what version of each dependency to check out, and
 # where.
 #
 # For more information, please refer to the official documentation:
 #   https://sites.google.com/a/chromium.org/dev/developers/how-tos/get-the-code
 #
 # When adding a new dependency, please update the top-level .gitignore file
 # to list the dependency's destination directory.
 #
@@ skipping 190 matching lines @@
   'src/third_party/usrsctp/usrsctplib':
     Var('chromium_git') + '/external/github.com/sctplab/usrsctp' + '@' + 'c60ec8b35c3fe6027d7a3faae89d1c8d7dd3ce98',
 
   'src/third_party/libsrtp':
    Var('chromium_git') + '/chromium/deps/libsrtp.git' + '@' + '720780acf8fa41c4a6ad515d0382d62f8f5195eb', # from svn revision 295151
 
   'src/third_party/yasm/source/patched-yasm':
    Var('chromium_git') + '/chromium/deps/yasm/patched-yasm.git' + '@' + '7da28c6c7c6a1387217352ce02b31754deb54d2a',
 
   'src/third_party/libjpeg_turbo':
-   Var('chromium_git') + '/chromium/deps/libjpeg_turbo.git' + '@' + '51655203fbc949e6423dcd13ce22fe30ab5b5ea2',
+   Var('chromium_git') + '/chromium/deps/libjpeg_turbo.git' + '@' + '414f2433e6634942b9ceea9450bdc21dcc5520cf',
 
   'src/third_party/flac':
    Var('chromium_git') + '/chromium/deps/flac.git' + '@' + '812243a85937e06102ba312c6caf8823e243b35b',
 
   'src/third_party/flatbuffers/src':
    Var('chromium_git') + '/external/github.com/google/flatbuffers.git' + '@' + '6f751d5d26fd566f8c9060358101a2596677f9cf',
 
   'src/third_party/pyftpdlib/src':
     Var('chromium_git') + '/external/pyftpdlib.git' + '@' + '2be6d65e31c7ee6320d059f581f05ae8d89d7e45',
 
@@ skipping 623 matching lines @@
   {
     # A change to a .gyp, .gypi, or to GYP itself should run the generator.
     'name': 'gyp',
     'pattern': '.',
     'action': ['python', 'src/build/gyp_chromium', '--running-as-hook'],
   },
 ]
 
 # ANGLE manages DEPS that it also owns the build files for, such as dEQP.
 recursedeps = [("src/third_party/angle", "DEPS.chromium")]