Fix margin on saved draft

GrMarkdown migration removed GrFormattedText's :host {display: block;}
rule, and margin did not apply to display: inline element. Block should
instead be set in GrComment who is the one adding the margin.

https://imgur.com/a/2bnzcEd

Release-Notes: skip
Change-Id: I0edb32ca51e9ab960cbb20f55108533bb9cc29db

polygerrit-ui/app/elements/shared/gr-comment/gr-comment.ts

diff --git a/polygerrit-ui/app/elements/shared/gr-comment/gr-comment.ts b/polygerrit-ui/app/elements/shared/gr-comment/gr-comment.ts
index 6f40254..ad2daf5 100644
--- a/polygerrit-ui/app/elements/shared/gr-comment/gr-comment.ts
+++ b/polygerrit-ui/app/elements/shared/gr-comment/gr-comment.ts
@@ -490,6 +490,7 @@
           width: unset;
         }
         .draft gr-formatted-text.message {
+          display: block;
           margin-bottom: var(--spacing-m);
         }
         .portedMessage {