The last bit of rolling back commandlineflag categories:
remove the 'categories' field from CommandLineFlagInfo.  (Note
the code to fill this field was removed from
FillComandLineFlagInfo previously, so it's been an empty
string for some time now.)

R=ncalvin
DELTA=1  (0 added, 1 deleted, 0 changed)


Revision created by MOE tool push_codebase.
MOE_MIGRATION=3616


git-svn-id: https://gflags.googlecode.com/svn/trunk@70 6586e3c6-dcc4-952a-343f-ff74eb82781d