Remove obsolete flag `render_markdown`

Release-Notes: skip
Change-Id: I4a3c45128271e3b17a054719ab29511732f4f56d

polygerrit-ui/app/services/flags/flags.ts

diff --git a/polygerrit-ui/app/services/flags/flags.ts b/polygerrit-ui/app/services/flags/flags.ts
index 508bef0..93a82697d 100644
--- a/polygerrit-ui/app/services/flags/flags.ts
+++ b/polygerrit-ui/app/services/flags/flags.ts
@@ -20,6 +20,5 @@
   DIFF_RENDERING_LIT = 'UiFeature__diff_rendering_lit',
   PUSH_NOTIFICATIONS = 'UiFeature__push_notifications',
   SUGGEST_EDIT = 'UiFeature__suggest_edit',
-  RENDER_MARKDOWN = 'UiFeature__render_markdown',
   REBASE_CHAIN = 'UiFeature__rebase_chain',
 }