api: Fix number of signals

We have 10 signals, not 11.  Setting 11 results in reading
beyond the signals defined and trying to create signals with
NULL values.

src/lurch_api.c

@@ -564,7 +564,7 @@ typedef enum {
  * When adding a new signal: increase this number and add the name, handler function, and handler function type
  * to the respective array.
  */
-#define NUM_OF_SIGNALS 11
+#define NUM_OF_SIGNALS 10
 
 const char * signal_names[NUM_OF_SIGNALS] = {
   "lurch-id-list",