doc_src: Continue the slog through the letter F.

We are using only :: in a synopsis for fishscript examples given
of the command being documented.

doc_src/cmds/fish_status_to_signal.rst

@@ -6,6 +6,7 @@ fish_status_to_signal - convert exit codes to human-friendly signals
 Synopsis
 --------
 
+``fish_status_to_signal`` *NUM*
 ::
 
     function fish_prompt
@@ -26,4 +27,4 @@ Example
     >_ sleep 5
     ^C⏎
     >_ fish_status_to_signal $status
-    SIGINT
+    SIGINT