Remove mut self reference from LogExporter::export() method. (open-telemetry#2380)

Author: lalitb

benches/logs.rs

@@ -34,7 +34,7 @@ struct NoopExporter {
 
 #[async_trait]
 impl LogExporter for NoopExporter {
-    async fn export(&mut self, _: LogBatch<'_>) -> LogResult<()> {
+    async fn export(&self, _: LogBatch<'_>) -> LogResult<()> {
         LogResult::Ok(())
     }
 

src/layer.rs

@@ -247,7 +247,7 @@ mod tests {
 
     #[async_trait]
     impl LogExporter for ReentrantLogExporter {
-        async fn export(&mut self, _batch: LogBatch<'_>) -> LogResult<()> {
+        async fn export(&self, _batch: LogBatch<'_>) -> LogResult<()> {
             // This will cause a deadlock as the export itself creates a log
             // while still within the lock of the SimpleLogProcessor.
             warn!(name: "my-event-name", target: "reentrant", event_id = 20, user_name = "otel", user_email = "[email protected]");