Autosuggest in extension search suggests already used filters

[RMacfarlane]

Testing #55386

When using the '...' menu to add sort filter options, the option becomes disabled in the menu, preventing it from being added twice from that UI.

I think it would be nice if the suggestions behaved similarly, not suggesting filters that are already present in the input.

VS Code version: Code - Insiders 1.26.0-insider (0707dd4, 2018-07-31T05:18:06.861Z)
OS version: Windows_NT x64 10.0.17134