libmain: drop categories for dry-run and json args

36c4d6f592 introduced it commented. Zero
explanation why.

horrors suggested to drop it entirely because it hide the options in
categories but they are pretty common and we should make as much visible
as possible.

Change-Id: I09894b5ba0f2b2cce5869136914289fed034fce3
Signed-off-by: Raito Bezarius <raito@lix.systems>

lix/libmain/common-args.hh

@@ -6,7 +6,6 @@
 
 namespace nix {
 
-//static constexpr auto commonArgsCategory = "Miscellaneous common options";
 static constexpr auto loggingCategory = "Logging-related options";
 static constexpr auto miscCategory = "Miscellaneous global options";
 
@@ -29,7 +28,6 @@ struct MixDryRun : virtual Args
         addFlag({
             .longName = "dry-run",
             .description = "Show what this command would do without doing it.",
-            //.category = commonArgsCategory,
             .handler = {&dryRun, true},
         });
     }
@@ -44,7 +42,6 @@ struct MixJSON : virtual Args
         addFlag({
             .longName = "json",
             .description = "Produce output in JSON format, suitable for consumption by another program.",
-            //.category = commonArgsCategory,
             .handler = {&json, true},
         });
     }