Update dependency prettier to v2

[renovate]

This PR contains the following updates:

Package	Change	Age	Adoption	Passing	Confidence
prettier (source)	1.19.1 -> 2.6.2

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[codecov]

Codecov Report

Merging #382 (741796b) into master (58a7022) will increase coverage by 0.19%.
The diff coverage is 80.95%.

@@            Coverage Diff             @@
##           master     #382      +/-   ##
==========================================
+ Coverage   73.96%   74.15%   +0.19%     
==========================================
  Files          19       19              
  Lines         653      654       +1     
  Branches      112      112              
==========================================
+ Hits          483      485       +2     
+ Misses        144      143       -1     
  Partials       26       26              

Impacted Files	Coverage Δ
server/src/util/fs.ts	75.00% <ø> (ø)
vscode-client/src/server.ts	0.00% <0.00%> (ø)
server/src/server.ts	57.44% <83.33%> (ø)
server/src/analyser.ts	83.43% <100.00%> (+0.19%)	⬆️
server/src/executables.ts	93.75% <100.00%> (ø)
server/src/linter.ts	88.40% <100.00%> (ø)
server/src/util/array.ts	100.00% <100.00%> (ø)
server/src/util/flatten.ts	100.00% <100.00%> (ø)
server/src/util/sh.ts	88.46% <100.00%> (ø)
server/src/util/tree-sitter.ts	100.00% <100.00%> (ø)

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