pidgin/pidgin

bitbucket-pipelines.yml: Change `make check` to `make distcheck`

Now that `make distcheck` should succeed, we can just use it as it
internally does `make check`. This patch changes the BitBucket
pipeline file to do so.
For information on writing a plugin for Purple, Pidgin or Finch, go
https://developer.pidgin.im and click on API. From there, see the
HOWTOs in the "Related Pages" section.
You can also generate this documentation locally by passing
"--enable-gtk-doc" to ./configure, then running "make" in the source tree.
The documentation will be in the doc/reference/*/html directories.