[VPlan] Don't print interleave group insert position. (#200023)
This patch updates interleave group printing to drop the insert
position. It does not add any information (the position of the
interleave group is determined by the position in VPlan), and for stores
we currently were printing <badref> anyways (trying to print a value
with void type).
PR: https://github.com/llvm/llvm-project/pull/200023