shell-util: Remove shell_breakpoint

A near identical function appears in gjs, in the "system" module:

    const System = imports.system;
    System.breakpoint();

src/shell-util.c

@@ -678,18 +678,6 @@ shell_get_file_contents_utf8_sync (const char *path,
   return contents;
 }
 
-/**
- * shell_breakpoint:
- *
- * Using G_BREAKPOINT(), interrupt the current process.  This is useful
- * in conjunction with a debugger such as gdb.
- */
-void
-shell_breakpoint (void)
-{
-  G_BREAKPOINT ();
-}
-
 /**
  * shell_parse_search_provider:
  * @data: description of provider

src/shell-util.h

@@ -39,8 +39,6 @@ gboolean shell_write_string_to_stream          (GOutputStream    *stream,
 char    *shell_get_file_contents_utf8_sync     (const char       *path,
                                                 GError          **error);
 
-void     shell_breakpoint                      (void);
-
 gboolean shell_parse_search_provider           (const char       *data,
                                                 char            **name,
                                                 char            **url,