Update release milestone the feature was introduced

doc/user/project/releases/index.md

@@ -147,7 +147,7 @@ You can also edit an existing tag to add release notes:
 
 ## Release Evidence
 
-> [Introduced](https://gitlab.com/gitlab-org/gitlab/issues/26019) in GitLab 12.5.
+> [Introduced](https://gitlab.com/gitlab-org/gitlab/issues/26019) in GitLab 12.6.
 
 Each time a new release is created, specific related data is collected in
 parallel. This dataset will be a snapshot this new release (including linked
@@ -155,7 +155,7 @@ milestones and issues) at moment of creation. Such collection of data will
 provide a chain of custody and facilitate processes like external audits, for example.
 
 The gathered Evidence data is stored in the database upon creation of a new
-release as a JSON object. In GitLab 12.5, a link to
+release as a JSON object. In GitLab 12.6, a link to
 the Evidence data is provided for [each Release](#releases-list).
 
 Here's what this object can look like: