lisa.trace: Only show closest matches in MissingTraceEventError

FEATURE

Do not show the full set of available events as it typically is very
large and makes the output hard to read. Instead, only show the closest
matches for the events that are missing.

lisa/trace.py

@@ -5591,9 +5591,8 @@ def __str__(self):
                 )
                 if matches
             }
-            available = '. Closest available matches are: {}. Available events are: {}'.format(
+            available = '. Closest available matches are: {}'.format(
                 ', '.join(sorted(closest)),
-                ', '.join(sorted(available))
             )
         else:
             available = ''