docs: fix mandoc issue in pmdaopenmetrics.1 man page
docs: fix mandoc issue in pmdaopenmetrics.1 man page

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adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp