Fix gerrit mimetype references
Fix gerrit mimetype references

Files for direct downloads are text, not application specific.
Gerrit mimetype setting documentation:
https://gerrit-review.googlesource.com/Documentation/config-gerrit.html#mimetype

Change-Id: I5b7b98c098176805f432bce6c15705666e34e251

open-switch/infra_puppet-gerrit,dhiana/puppet-gerrit,open-switch/infra_puppet-gerrit,dhiana/puppet-gerrit,dhiana/puppet-gerrit,open-switch/infra_puppet-gerrit