Build: spec: remove redundant "AutoReqProv: on" tagging

References:
https://en.opensuse.org/openSUSE:Specfile_guidelines#Metadata_Tags
+ there is a better approach to intervene:
https://docs-old.fedoraproject.org/en-US/Fedora_Draft_Documentation/0.1/html/RPM_Guide/ch-packaging-guidelines.html#id670777
+ plain fact it's "on" by default (~1996, rpm-4.4):
https://github.com/rpm-software-management/rpm/commit/b669dad0f#diff-e6636f985597aa708a59eda2ee4c8cedR834