Update 1.2.1 release notes (#3601) (#3603)

Author: charith-elastic

docs/release-notes/1.2.1.asciidoc

@@ -17,6 +17,8 @@
 [float]
 === Bug fixes
 
+* Avoid pollution of map constants via defensive copy {pull}3599[#3599]
+* Fix filebeat securityContext in recipes {pull}3596[#3596]
 * Check if CA Secret is expected before validating its name {pull}3527[#3527] (issue: {issue}3523[#3523])
 * Fix memory corruption from pod template validation {pull}3524[#3524] (issue: {issue}3421[#3421])