[DOCS] Rename Glossary (#71222)

Changes title from "Glossary of terms" to "Glossary."
"Glossary of terms" is redundant.

docs/reference/glossary.asciidoc

@@ -8,7 +8,7 @@ https://github.com/elastic/stack-docs/tree/master/docs/en/glossary
 
 [glossary]
 [[glossary]]
-= Glossary of terms
+= Glossary
 
 [glossary]
 [[glossary-analysis]] analysis::