Remove LbPowheg because it doesn't compile on gcc9
The removal is temporary and will only be released if a fix is not deployed before deploying v54r0. In case this MR will be reverted for a future release.
Closes LHCBGAUSS-1929
The removal is temporary and will only be released if a fix is not deployed before deploying v54r0. In case this MR will be reverted for a future release.
Closes LHCBGAUSS-1929