fix(docs): correct `--no-ff` -> `--ff-only`

The `--no-ff` flag always creates a merge commit; that's the opposite of
what we meant when this documentation was updated. Use `--ff-only` to
require fast-forwards pulls only.

Change-Id: Ia49ddccbfc998e403e900e9fa86f55129fe521b3
Signed-off-by: Chris Kay <chris.kay@arm.com>
1 file changed