Update dependency grunt-contrib-concat to v2

This MR contains the following updates:

Package	Type	Update	Change
grunt-contrib-concat	optionalDependencies	major	^1.0.1 -> ^2.0.0
grunt-contrib-concat	optionalDependencies	major	^1.0.0 -> ^2.0.0

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Release Notes

gruntjs/grunt-contrib-concat (grunt-contrib-concat)

v2.1.0

Compare Source

• Update readme 1437c62
• Merge pull request #​195 from gruntjs/new-deps-3 5bb6ed3
• Update deps e2e9345
• Merge pull request #​194 from gruntjs/dependabot/npm_and_yarn/minimist-1.2.6 021d809
• Bump minimist from 1.2.5 to 1.2.6 b43b373

v2.0.0

Compare Source

• Merge pull request #​192 from gruntjs/release-2 de2b0e9
• Release docs 2f2aeff
• Merge pull request #​191 from gruntjs/update-deps-oct 63a42a8
• Update CI 4c4fab8
• Update dependencies 71d6edd
• Merge pull request #​176 from alexjking/fix-browserify-sourcemap-regex 9054b14
• fix(sourcemap-regex): fix regex to match browserify sorucemap charset b1cf785

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