[DOCS] Fix typo in 7.15 release highlights (#78426)

Author: jessepeterman

docs/reference/release-notes/highlights.asciidoc

@@ -29,7 +29,7 @@ Other versions:
 [discrete]
 === Index disk usage API 
 There's a new API that supports analyzing the disk usage of each field of an
-index, including the entire index itself. The the API estimates the disk usage
+index, including the entire index itself. The API estimates the disk usage
 of a field by iterating over its content and tracking the number of bytes read.
 Refer to {ref}/indices-disk-usage.html[analyze index disk usage API].
 
@@ -53,4 +53,4 @@ Refer to {ref}/runtime-examples.html#runtime-examples-grok-composite[define a co
 // [discrete]
 // === Heading
 //
-// Description.
+// Description.