Remove --debug from collectArguments(), it's already a proper option

Author: eregon

src/launcher/java/org/truffleruby/launcher/RubyLauncher.java

@@ -139,7 +139,7 @@ protected void collectArguments(Set<String> options) {
                 "-a",
                 "-c",
                 "-C",
-                "-d", "--debug",
+                "-d",
                 "-e",
                 "-E", "--encoding",
                 "-F",