7.17.21 Release notes (#5140)

* First draft

* Fixed ver

Author: nastasha-solomon

docs/release-notes.asciidoc

@@ -3,6 +3,7 @@
 
 This section summarizes the changes in each release.
 
+* <<release-notes-7.17.21, {elastic-sec} version 7.17.21>>
 * <<release-notes-7.17.20, {elastic-sec} version 7.17.20>>
 * <<release-notes-7.17.19, {elastic-sec} version 7.17.19>>
 * <<release-notes-7.17.18, {elastic-sec} version 7.17.18>>

docs/release-notes/7.17.asciidoc

@@ -1,6 +1,16 @@
 [[release-notes-header-7.17.0]]
 == 7.17
 
+[discrete]
+[[release-notes-7.17.21]]
+=== 7.17.21
+
+[discrete]
+[[bug-fixes-7.17.21]]
+==== Bug fixes and enhancements
+
+There are no user-facing changes in the 7.17.21 release.
+
 [discrete]
 [[release-notes-7.17.20]]
 === 7.17.20
@@ -19,7 +29,7 @@ There are no user-facing changes in the 7.17.20 release.
 [[bug-fixes-7.17.19]]
 ==== Bug fixes and enhancements
 
-* Adds file and size constraints to value lists ({pull}176074[#176074]).
+* Adds file and size constraints to value lists ({kibana-pull}176074[#176074]).
 
 [discrete]
 [[release-notes-7.17.18]]