Remove a no-longer-used file (build/support/support.gyp).

(It was always useless and also incorrect, anyway.) Mention of it was removed
from chrome_dll.gypi by Nico in r72087, but he was too lazy to remove the file

TEST=everything builds, and the aforementioned file is no longer there
Review URL:

git-svn-id: 4ff67af0-8c30-449e-8e8b-ad334ec8d88c
1 file changed
tree: 4b825dc642cb6eb9a060e54bf8d69288fbee4904

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