Bump github.com/alecthomas/chroma from 0.8.2 to 0.9.1

Bumps [github.com/alecthomas/chroma](https://github.com/alecthomas/chroma) from 0.8.2 to 0.9.1.
- [Release notes](https://github.com/alecthomas/chroma/releases)
- [Changelog](https://github.com/alecthomas/chroma/blob/master/.goreleaser.yml)
- [Commits](alecthomas/chroma@v0.8.2...v0.9.1)

Signed-off-by: dependabot[bot] <support@github.com>

go.mod

@@ -4,11 +4,10 @@ go 1.15
 
 require (
 	github.com/Jeffail/tunny v0.0.0-20210126202424-1b37d6cb867a
-	github.com/alecthomas/chroma v0.8.2
+	github.com/alecthomas/chroma v0.9.1
 	github.com/armon/go-metrics v0.3.6 // indirect
 	github.com/buildkite/terminal-to-html v3.2.0+incompatible
 	github.com/cpuguy83/go-md2man/v2 v2.0.0 // indirect
-	github.com/dlclark/regexp2 v1.4.0 // indirect
 	github.com/fatih/color v1.10.0 // indirect
 	github.com/golang/protobuf v1.4.3 // indirect
 	github.com/gorilla/mux v1.8.0
@@ -24,7 +23,6 @@ require (
 	github.com/hashicorp/yamux v0.0.0-20200609203250-aecfd211c9ce // indirect
 	github.com/karlseguin/ccache v2.0.3+incompatible
 	github.com/karlseguin/expect v1.0.1 // indirect
-	github.com/magefile/mage v1.11.0 // indirect
 	github.com/mattn/go-runewidth v0.0.10 // indirect
 	github.com/mitchellh/colorstring v0.0.0-20190213212951-d06e56a500db
 	github.com/mitchellh/copystructure v1.1.1 // indirect