Remove kdbus custom endpoint support

This feature will not be used anytime soon, so remove a bit of cruft.

The BusPolicy= config directive will stay around as compat noop.

src/basic/exit-status.c

@@ -147,9 +147,6 @@ const char* exit_status_to_string(ExitStatus status, ExitStatusLevel level) {
                 case EXIT_MAKE_STARTER:
                         return "MAKE_STARTER";
 
-                case EXIT_BUS_ENDPOINT:
-                        return "BUS_ENDPOINT";
-
                 case EXIT_SMACK_PROCESS_LABEL:
                         return "SMACK_PROCESS_LABEL";
                 }

src/basic/exit-status.h

@@ -77,7 +77,6 @@ typedef enum ExitStatus {
         EXIT_RUNTIME_DIRECTORY,
         EXIT_MAKE_STARTER,
         EXIT_CHOWN,
-        EXIT_BUS_ENDPOINT,
         EXIT_SMACK_PROCESS_LABEL,
 } ExitStatus;