Change border-color everywhere to #e8e8e8

Given the crazy amount of borders that we are using on the dashboard
and the change page, I think we have to tone this color down a little.

https://imgur.com/a/9klCFBe

Change-Id: Ie535c705f7eea0d5f5806a3d8e41411a764e40fe
diff --git a/polygerrit-ui/app/styles/themes/app-theme.html b/polygerrit-ui/app/styles/themes/app-theme.html
index fc7478b..db49822 100644
--- a/polygerrit-ui/app/styles/themes/app-theme.html
+++ b/polygerrit-ui/app/styles/themes/app-theme.html
@@ -77,7 +77,7 @@
   --vote-color-rejected: #f7a1ad;
 
   /* misc colors */
-  --border-color: #dadce0;
+  --border-color: #e8e8e8;
 
   /* fonts */
   --font-family: 'Roboto', -apple-system, BlinkMacSystemFont, 'Segoe UI', Helvetica, Arial, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol';