editor: Use a small multiselect buffer zone

[youknowriad]

fixes #2646

I'm not sure why this buffer zone exists in the first place, but making it smaller makes it a better experience IMO.

[codecov]

Codecov Report

Merging #2695 into master will not change coverage.
The diff coverage is 0%.

@@           Coverage Diff           @@
##           master    #2695   +/-   ##
=======================================
  Coverage   33.16%   33.16%           
=======================================
  Files         182      182           
  Lines        5530     5530           
  Branches      963      963           
=======================================
  Hits         1834     1834           
  Misses       3130     3130           
  Partials      566      566

Impacted Files	Coverage Δ
editor/modes/visual-editor/block-list.js	0% <0%> (ø)	⬆️

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[aduth]

Not sure I feel entirely comfortable reviewing something when we don't know the original intent and therefore the impact of the changes 😄

[aduth]

cc @iseulde

[ellatrix]

I agree with this change. May need more tweaking. @jasmussen suggested setting it really high. back when it was first added, but I agree it's weird on small blocks.

[jasmussen]

Definitely tune it if need be. I did suggest setting it SUPER high, because I feel like it's easier to pull back from up high, than the other way around.