gh-102809: Remove Misc/gdbinit (#102854)

Looks like the consensus is that we don't need this file anymore.
Old version can be always found here: https://github.com/python/cpython/blob/094cf392f49d3c16fe798863717f6c8e0f3734bb/Misc/gdbinit

Author: sobolevn

Misc/NEWS.d/next/Tools-Demos/2023-03-21-01-27-07.gh-issue-102809.2F1Byz.rst

@@ -0,0 +1 @@
+``Misc/gdbinit`` was removed.