Delete integration code for git-link and git-timemachine, which is
superseded by upstream changes to git-link committed in August 2016:
433ba1dba7
* CHANGELOG.develop: Add an entry for this change.
* layers/+source-control/git/funcs.el (spacemacs/git-link-copy-url-only):
Replace call to spacemacs/git-link with a call to git-link.
(spacemacs/git-link-commit-copy-url-only): Replace call to
spacemacs/git-link-commit with a call to git-link-commit.
(spacemacs/git-link, spacemacs/git-link-commit): Delete functions.
* layers/+source-control/git/packages.el (git/init-git-link): Replace
binding to spacemacs/git-link with a binding to git-link.
8d6f736209