Add !inSnippetMode context on Tab for acceptSelectedSuggestion shortcut

[sedyh]

There is a conflict between jump-to-next-placeholder and accept-suggestion shortcut.
Right now, pressing the tab key while editing a snipper will stop snippet mode and accept the first suggestion.

This can be easily fixed by adding additional context for this key:

I think the editor should have this by default.

Related issues:
#50776