man: rename rst2man.py -> rst2man

sphinx_rtd_theme 3.0.0 added "support for docutils >0.18, <0.22." [1].
Prior releases limited docutils to <0.21.

docutils 0.21 added "entry points (without the .py extension) instead of
installing the rst2*.py front end tools in the binary PATH." [2]

So change the rst2man call from rst2man.py to rst2man in the man
Makefile.

[1] https://sphinx-rtd-theme.readthedocs.io/en/stable/changelog.html
[2] https://docutils.sourceforge.io/RELEASE-NOTES.html#release-0-21-2024-04-09

Signed-off-by: Bastian Krause <bst@pengutronix.de>

Author: Bastian-Krause

man/Makefile

@@ -2,7 +2,7 @@ PAGES := labgrid-client.1 labgrid-coordinator.1 labgrid-exporter.1 labgrid-devic
 COMPRESSED := labgrid-client.1.gz labgrid-coordinator.1.gz labgrid-exporter.1.gz labgrid-device-config.5.gz labgrid-pytest.7.gz labgrid-suggest.1.gz
 
 %.1 %.5 %.7: %.rst
-	rst2man.py $< >$@.tmp
+	rst2man $< >$@.tmp
 	mv -f $@.tmp $@
 
 %.gz : %