Issue Type: Bug

When poping a stash and there are merge conflicts between the stash and current code, even after the conflict is resolved, the pop'ed stash isn't dropped from the stash list.
The only way to drop a stash in vscode, AFAIK, is by successfully merging a stash, meaning that if a stash is no longer relevant (only conflicts, never merged), it can never be dropped from within vscode, only by a terminal command.

my suggestion is: when there are conflicts, let the user choose whether to resolve the conflicts or to just drop the stash.

VS Code version: Code 1.35.1 (c7d83e5, 2019-06-12T14:30:02.622Z)
OS version: Windows_NT x64 10.0.17763