NIT refactor using directives usage in gcbenchmark: get rid of unnecessary commas and double quote escapes

Author: Gedochao

gcbenchmark/gcbenchmark.scala

@@ -1,6 +1,6 @@
-//> using dep "com.lihaoyi::os-lib:0.9.1"
-//> using dep "com.lihaoyi::pprint:0.8.1"
-//> using scala "2.13"
+//> using dep com.lihaoyi::os-lib:0.9.1
+//> using dep com.lihaoyi::pprint:0.8.1
+//> using scala 2.13
 
 // Usage: scala-cli gcbenchmark.scala -- <path_to_scala_cli_executable>