[lldb] Add missing whitespace in help text

(cherry picked from commit 2b7e9d2)

Author: adrian-prantl

lldb/source/Interpreter/CommandInterpreter.cpp

@@ -850,7 +850,7 @@ void CommandInterpreter::LoadCommandDictionary() {
           "argument displays at most that many frames. The argument 'all' "
           "displays all threads. Use 'settings set frame-format' to customize "
           "the printing of individual frames and 'settings set thread-format' "
-          "to customize the thread header. Frame recognizers may filter the"
+          "to customize the thread header. Frame recognizers may filter the "
           "list. Use 'thread backtrace -u (--unfiltered)' to see them all.",
           "bt [<digit> | all]", 0, false));
   if (bt_regex_cmd_up) {