Update BookieInitializationTest assertion for slog message text

The slog conversion in this PR changed the exception-handler log message
from "Triggered exceptionHandler of Component: {}" (with placeholder)
to "Triggered exceptionHandler of Component" (component name moved to
a structured attr). Drop the trailing colon from the test's substring
match so it matches the new literal message.

Author: merlimat

bookkeeper-server/src/test/java/org/apache/bookkeeper/bookie/BookieInitializationTest.java

@@ -827,7 +827,7 @@ public void testBookieStartException() throws Exception {
          */
         loggerOutput.expect((List<LoggingEvent> logEvents) -> {
             assertThat(logEvents,
-                    hasItem(hasProperty("message", containsString("Triggered exceptionHandler of Component:"))));
+                    hasItem(hasProperty("message", containsString("Triggered exceptionHandler of Component"))));
         });
     }