[E&A] Makes EIS availability information more granular (#3120)

## Overview

This PR changes the `applies_to` tags in the EIS conceptual page to make
it clear that this feature is not available on self-managed
installations.

Author: szabosteve

explore-analyze/elastic-inference/eis.md

@@ -1,8 +1,10 @@
 ---
 navigation_title: Elastic Inference Service (EIS)
 applies_to:
-  stack: ga 9.0
+  stack: ga
   serverless: ga
+  deployment:
+    self: unavailable
 ---
 
 # Elastic {{infer-cap}} Service [elastic-inference-service-eis]

explore-analyze/elastic-inference/inference-api.md

@@ -30,7 +30,7 @@ The following section lists the default {{infer}} endpoints, identified by their
 
 ### Default endpoints for Elastic {{infer-cap}} Service (EIS)
 
-- `.elser-2-elastic`: uses the [ELSER](/explore-analyze/machine-learning/nlp/ml-nlp-elser.md) trained model as an Elastic {{infer-cap}} Service for `sparse_embedding` tasks (recommended for English language text). The `model_id` is `.elser_model_2`. {applies_to}`stack: preview 9.1` {applies_to}`serverless: preview`
+- `.elser-2-elastic`: uses the [ELSER](/explore-analyze/machine-learning/nlp/ml-nlp-elser.md) trained model as an Elastic {{infer-cap}} Service for `sparse_embedding` tasks (recommended for English language text). The `model_id` is `.elser_model_2`. {applies_to}`stack: preview 9.1` {applies_to}`self: unavailable` {applies_to}`serverless: preview`
 
 ### Default endpoints used on ML-nodes