Rename VR plugins
Due to these MR: paraview!5546 (merged) paraview!5649 (merged), flags needed to be renamed.
For the openvr plugin i changed only the flags not the library name too (the actual openvr).
cc: @ken-martin @mwestphal @tiffany.chhim @cory.quammen @scott.wittenburg
Edited by Spiros Tsalikis