Remove unneeded TODOs

These commands have been confirmed to have no arguments.

src/commands/debug.rs

@@ -18,7 +18,6 @@ impl WholeStreamCommand for Debug {
     }
 
     fn signature(&self) -> Signature {
-        // TODO: Signature?
         Signature::build("debug")
     }
 }

src/commands/ps.rs

@@ -20,7 +20,6 @@ impl WholeStreamCommand for PS {
     }
 
     fn signature(&self) -> Signature {
-        // TODO: Signature?
         Signature::build("ps")
     }
 }

src/commands/shells.rs

@@ -19,7 +19,6 @@ impl WholeStreamCommand for Shells {
     }
 
     fn signature(&self) -> Signature {
-        // TODO: Signature?
         Signature::build("shells")
     }
 }

src/commands/sort_by.rs

@@ -18,7 +18,6 @@ impl WholeStreamCommand for SortBy {
     }
 
     fn signature(&self) -> Signature {
-        // TODO: Signature?
         Signature::build("sort-by")
     }
 }