pr: close invalid, or non-applicable Github PRs

PR #1 -> too old to merge 4.2 on master now
PR #4 -> too old to merge 4.3 on master now
PR #5 -> source repo/branch deleted, not available now

This closes #1
This closes #4
This closes #5

This is an empty git commit.

Signed-off-by: Rohit Yadav <rohit.yadav@shapeblue.com>