fix a wrong comment.

[guanjianzhe]

1. "let g:override_spf13_bundles = 1" should be placed in
".vimrc.before.local", since ".vimrc.bundles.local" source too late.
2. ".vimrc.before.local" is the only choice for this local customize.

At last, I have verified this.

Signed-off-by: guanjianzhe [email protected]

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