Fixing the counter for indexing pipelines

It was stuck to 0 because I forgot to increment the guard upon creation.

Author: fulmicoton-dd

quickwit/quickwit-indexing/src/actors/indexing_pipeline.rs

@@ -159,7 +159,8 @@ impl IndexingPipeline {
         let indexing_pipelines_gauge = crate::metrics::INDEXER_METRICS
             .indexing_pipelines
             .with_label_values([&params.pipeline_id.index_uid.index_id]);
-        let indexing_pipelines_gauge_guard = OwnedGaugeGuard::from_gauge(indexing_pipelines_gauge);
+        let mut indexing_pipelines_gauge_guard = OwnedGaugeGuard::from_gauge(indexing_pipelines_gauge);
+        indexing_pipelines_gauge_guard.add(1);
         let params_fingerprint = params.params_fingerprint;
         IndexingPipeline {
             params,