php-baikal: update to 0.6.0

pkgsrc changes:
---------------
  * Remove APACHE_{GROUP,USER} definition to appease pkglint.
  * Remove an executable permission to suppress a warning.

upstream changes:
-----------------
0.6.0 (2019-08-25)

    Added support for php 7.3
    REMOVED support for php 5.x
    Enabled event invitation plugin
    Enabled calendar sharing plugin
    Ships with sabre/dav 4.0.1

0.5.3 (2019-05-13)

    Added confirmation page before upgrading to prevent aborting upgrades accidentally
    Ships with sabre/dav 3.2.3

0.5.2 (2019-04-26)

    Fixed creating new users/calendars
    New front page
    Increased timeout for database upgrades
    Ships with sabre/dav 3.2.3

0.5.1 (2019-04-21)

    Fixed authentication bypass
    Upgraded sabre/dav to version 3.2.3
    Support for PHP 7.2

(triaxx)