Update dependencies to latest versions

vendor/github.com/alecthomas/chroma/coalesce.go

@@ -6,17 +6,17 @@ func Coalesce(lexer Lexer) Lexer { return &coalescer{lexer} }
 type coalescer struct{ Lexer }
 
 func (d *coalescer) Tokenise(options *TokeniseOptions, text string) (Iterator, error) {
-	var prev *Token
+	var prev Token
 	it, err := d.Lexer.Tokenise(options, text)
 	if err != nil {
 		return nil, err
 	}
-	return func() *Token {
-		for token := it(); token != nil; token = it() {
+	return func() Token {
+		for token := it(); token != (EOF); token = it() {
 			if len(token.Value) == 0 {
 				continue
 			}
-			if prev == nil {
+			if prev == EOF {
 				prev = token
 			} else {
 				if prev.Type == token.Type && len(prev.Value) < 8192 {
@@ -29,7 +29,7 @@ func (d *coalescer) Tokenise(options *TokeniseOptions, text string) (Iterator, e
 			}
 		}
 		out := prev
-		prev = nil
+		prev = EOF
 		return out
 	}, nil
 }