Fix up some messages about sampling wiki links

Signed-off-by: Tudor Brindus <tbrindus@janestreet.com>

core/collection_mode.ml

@@ -87,7 +87,7 @@ let param =
       no_arg
       ~doc:
         "Use stacktrace sampling instead of Intel PT. If Intel PT is not available, \
-         magic-trace will default to this."
+         magic-trace will default to this. For more info: https://magic.trace.org/w/b"
   in
   select_collection_mode ~extra_events ~use_sampling
 ;;

src/callgraph_mode.ml

@@ -26,7 +26,7 @@ let param =
       " When magic-trace is running with sampling collection mode, this sets how it \
        should reconstruct callstacks. The options are [lbr]/[lbr-no-stitch]/[dwarf]/[fp] \
        or a sexp. Will default to [lbr] is available and [dwarf] otherwise. For more \
-       info: https://magic-trace.org/w/c"
+       info: https://magic-trace.org/w/b"
 ;;
 
 let to_perf_record_args = function

src/perf_tool_backend.ml

@@ -295,13 +295,13 @@ module Recording = struct
          | None, false ->
            Core.eprintf
              "Warning: [-callgraph-mode] is defaulting to [Dwarf] which may have high \
-              overhead and decoding time. For more info: https://magic-trace.org/w/c\n";
+              overhead and decoding time. For more info: https://magic-trace.org/w/b\n";
            return (Some Callgraph_mode.Dwarf)
          | None, true ->
            Core.eprintf
              "Warning: [-callgraph-mode] is defaulting to [Last_branch_record] which may \
               lose data and has limited callstack depth. For more info: \
-              https://magic-trace.org/w/c\n";
+              https://magic-trace.org/w/b\n";
            return (Some (Callgraph_mode.Last_branch_record { stitched = true }))
          | Some (Last_branch_record _), false ->
            Deferred.Or_error.error_string