Set the merge date on RFC 0025 stage 0 (#1447)

rfcs/text/0025-container-metric-fields.md

@@ -2,7 +2,7 @@
 <!-- Leave this ID at 0000. The ECS team will assign a unique, contiguous RFC number upon merging the initial stage of this RFC. -->
 
 - Stage: **0 (strawperson)** <!-- Update to reflect target stage. See https://elastic.github.io/ecs/stages.html -->
-- Date: **TBD** <!-- The ECS team sets this date at merge time. This is the date of the latest stage advancement. -->
+- Date: **2021-06-01** <!-- The ECS team sets this date at merge time. This is the date of the latest stage advancement. -->
 
 <!--
 As you work on your RFC, use the "Stage N" comments to guide you in what you should focus on, for the stage you're targeting.
@@ -112,6 +112,7 @@ Common Fields for Container Inventory Schema: https://github.com/elastic/beats/i
 <!-- An RFC should link to the PRs for each of it stage advancements. -->
 
 * Stage 0: https://github.com/elastic/ecs/pull/1441
+    * Stage 0 date correction: https://github.com/elastic/ecs/pull/1447
 
 <!--
 * Stage 1: https://github.com/elastic/ecs/pull/NNN