gnu: mcron: Update to 1.1 and deprecate "mcron2".

* gnu/packages/guile.scm (mcron): Update to 1.1.
[native-inputs]: Add TZDATA-FOR-TESTS.
[arguments]: New field.
(mcron2): Define using 'deprecated-package'.
* gnu/services/mcron.scm: Replace 'mcron2' with 'mcron'.
* doc/guix.texi (Scheduled Job Execution): Likewise.
* gnu/tests/base.scm (%mcron-os): Remove comment about mcron2.