Remove unused resource_maps from grd files.

These are only used if code needs to map a string like "IDR_FOO" to the
resource id IDR_FOO, which most code doesn't need to do. The majority of files
didn't add the generated .cc files to the build.

(Some files claimed that these outputs are needed to make MSVS stop rerunning
the grit step -- I believe that's because grit outputs are embedded into build
files at gyp time, and folks didn't try regypping after trying to remove these
lines.)

BUG=297672
NOTRY=true

Review URL: https://codereview.chromium.org/101983005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@242785 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 242785