Fix typo in vector docs where bit is not properly highlighted

Adds highlighting to `bit` as a possible option for the value
of `element_type`.

Author: dimitris-athanasiou

docs/reference/elasticsearch/mapping-reference/dense-vector.md

@@ -274,7 +274,7 @@ The following mapping parameters are accepted:
 $$$dense-vector-element-type$$$
 
 `element_type`
-:   (Optional, string) The data type used to encode vectors. The supported data types are `float` (default), `byte`, and bit.
+:   (Optional, string) The data type used to encode vectors. The supported data types are `float` (default), `byte`, and `bit`.
 
 ::::{dropdown} Valid values for element_type
 `float`

docs/reference/elasticsearch/mapping-reference/rank-vectors.md

@@ -90,7 +90,7 @@ The `rank_vectors` field type supports the following parameters:
 $$$rank-vectors-element-type$$$
 
 `element_type`
-:   (Optional, string) The data type used to encode vectors. The supported data types are `float` (default), `byte`, and bit.
+:   (Optional, string) The data type used to encode vectors. The supported data types are `float` (default), `byte`, and `bit`.
 
 ::::{dropdown} Valid values for element_type
 `float`