g2o: remove optional qt and libqglviewer options
g2o: remove optional qt and libqglviewer options

The optional qt dependency is not used
at all by the formula (at least for the moment).

libqglviewer has been boneyarded, this optional dependency
should already have been removed.

Closes #4659.

Signed-off-by: Jonathan Chang <0bd51b8a224feeddb634965eebae512adcd49a8d@gmail.com>

parcollet/homebrew-science,philippbayer/homebrew-science,andrewjpage/homebrew-science,maplesond/homebrew-science,quantumsteve/homebrew-science,dpo/homebrew-science,DabeDotCom/homebrew-science,pditommaso/homebrew-science,heuermh/homebrew-science