use Info level for excluded databases log message (#1003)

This is the only log message which didn't specify a level in the
postgres_exporter. I am unsure if this log message should be info or
debug, but leaning towards the more important since previously it would
just always log.

The way I validated this was the only non-leveled logger was via grep.
Both of these only returned this callsite previously:

  git grep 'logger\.Log'
  git grep '\.Log(' | grep -v level

Signed-off-by: Keegan Carruthers-Smith <keegan.csmith@gmail.com>

cmd/postgres_exporter/main.go

@@ -93,7 +93,7 @@ func main() {
 	}
 
 	excludedDatabases := strings.Split(*excludeDatabases, ",")
-	logger.Log("msg", "Excluded databases", "databases", fmt.Sprintf("%v", excludedDatabases))
+	level.Info(logger).Log("msg", "Excluded databases", "databases", fmt.Sprintf("%v", excludedDatabases))
 
 	if *queriesPath != "" {
 		level.Warn(logger).Log("msg", "The extended queries.yaml config is DEPRECATED", "file", *queriesPath)