Replace usage of #!/usr/bin/env python3 with #!/usr/bin/python3

Only three remaining scripts used this form, two of which are
for developers only and not shipped.

The shebang in ipa-ccache-sweeper will be converted to
"#!$(PYTHON) -I" in the build process.

Fixes: https://pagure.io/freeipa/issue/8941

Signed-off-by: Rob Crittenden <rcritten@redhat.com>
Reviewed-By: Rafael Guterres Jeffman <rjeffman@redhat.com>

install/tools/ipa-ccache-sweeper.in

@@ -1,4 +1,4 @@
-#!/usr/bin/env python3
+#!/usr/bin/python3
 
 # Based heavily on
 # https://github.com/gssapi/mod_auth_gssapi/blob/master/contrib/sweeper.py