Log instrumentation only when successful

Do not log "Instrumenting ..." when attempting to start an
instrumentation (the required dependency for which might not actually
be installed)

Instead, log "Instrumented ..." when an instrumentation is correctly
started.

src/appsignal/opentelemetry.py

@@ -192,7 +192,7 @@ def add_instrumentations(
     for name, adder in _adders.items():
         if name not in disable_list:
             try:
-                logger.info(f"Instrumenting {name}")
                 adder()
+                logger.info(f"Instrumented {name}")
             except ModuleNotFoundError:
                 pass