ports-mgmt/portlint: Update to 2.20.0

* Check for duplicate distinfo items [1]
* Remove vestiges of SVN [2]

[2] Switch to using `git status` to determine if a file is under git version
control.  Also, PL_SVN_IGNORE has been renamed to PL_GIT_IGNORE.

PR:		267168 [1]
		267145 [2]
Submitted by:	rodrigo [1]
Thanks to:	pauamma for the `git status` command [2]