[Docs] Edit semantic_text update instructions for clarity (#137345)

* [Docd] Update semantic_text update instructions for clarity

while reviewing #137340, I noticed this section was a little messy

refactored to use definition lists

* Clarify instructions on preserving embeddings

Author: leemthompo

docs/reference/elasticsearch/mapping-reference/semantic-text.md

@@ -424,20 +424,20 @@ POST test-index/_search
 
 ## Updates and partial updates for `semantic_text` fields [semantic-text-updates]
 
-When updating documents that contain `semantic_text` fields, it’s important to understand how inference is triggered:
+When updating documents that contain `semantic_text` fields, it's important to understand how inference is triggered:
 
-* **Full document updates**
-  When you perform a full document update, **all `semantic_text` fields will re-run inference** even if their values did not change. This ensures that the embeddings are always consistent with the current document state but can increase ingestion costs.
+Full document updates
+:   Full document updates re-run inference on all `semantic_text` fields, even if their values did not change. This ensures that embeddings remain consistent with the current document state but can increase ingestion costs.
 
-* **Partial updates using the Bulk API**
-  Partial updates that **omit `semantic_text` fields** and are submitted through the [Bulk API](https://www.elastic.co/docs/api/doc/elasticsearch/operation/operation-bulk) will **reuse the existing embeddings** stored in the index. In this case, inference is **not triggered** for fields that were not updated, which can significantly reduce processing time and cost.
+Partial updates using the Bulk API
+:   Partial updates submitted through the [Bulk API](https://www.elastic.co/docs/api/doc/elasticsearch/operation/operation-bulk) reuse existing embeddings when you omit `semantic_text` fields. Inference does not run for omitted fields, which can significantly reduce processing time and cost.
 
-* **Partial updates using the Update API**
-  When using the [Update API](https://www.elastic.co/docs/api/doc/elasticsearch/operation/operation-update) with a `doc` object that **omits `semantic_text` fields**, inference **will still run** on all `semantic_text` fields. This means that even if the field values are not changed, embeddings will be re-generated.
+Partial updates using the Update API
+:   Partial updates submitted through the [Update API](https://www.elastic.co/docs/api/doc/elasticsearch/operation/operation-update) re-run inference on all `semantic_text` fields, even when you omit them from the `doc` object. Embeddings are re-generated regardless of whether field values changed.
 
-If you want to avoid unnecessary inference and keep existing embeddings:
+To preserve existing embeddings and avoid unnecessary inference costs:
 
- * Use **partial updates through the Bulk API**.
+ * Use partial updates with the Bulk API.
  * Omit any `semantic_text` fields that did not change from the `doc` object in your request.
 
 ### Scripted updates