nir/lower_returns: Don't just change the type of a jump.
nir/lower_returns: Don't just change the type of a jump.

It doesn't give core NIR the opportunity to update predecessors and
successors.  Instead, we have to remove and re-insert the instruction.

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler