python, keygen: drop comments after %endif
    
    New RPMs (rpmbuild, rpmlint) print an ugly warning for this:
    warning: extra tokens at the end of %endif directive in line 106:  %endif # with python2
    warning: extra tokens at the end of %endif directive in line 140:  %endif # with python3
    warning: extra tokens at the end of %endif directive in line 160:  %endif # with python3
    warning: extra tokens at the end of %endif directive in line 206:  %endif # with python3
    warning: extra tokens at the end of %endif directive in line 213:  %endif # with python2
    
    Merges: #1029