If you cut and pasted the ansible.cfg section, the spelling of the
section header is incorrect:
s/ssh_connectin/ssh_connection/
Check that you don't have an old control socket lying around in
~/.ansible/cp/ between fixing that problem or otherwise updating your
ssh connection parameters and trying again.
Invoke ansible with the -vvvv flag to see what options are making it
to the invocation of ssh.
I created a github repo and tried this just now. I moved my existing
.ssh/config out of the way first and then created an ansible.cfg with
the misspelled section header. Running:
ansible rhel7 -m git -a 'repo=git@bitbucket.org:toshio/local-playbooks
dest=/var/tmp/plays'
Replicated your symptoms.
Fixing the section header and then making sure there was no control
socket still laying around in ~/.ansible/cp/ I then ran the above
ansible command and it was successful