Fix vertical alignment of text in diffs

- Adds changelog

app/assets/stylesheets/pages/diff.scss

@@ -72,6 +72,7 @@
       .line_holder td {
         line-height: $code-line-height;
         font-size: $code-font-size;
+        vertical-align: top;
 
         &.noteable_line {
           position: relative;

changelogs/unreleased/48902-fix-diff-vertical-alignment.yml

+---
+title: Fix vertical alignment of text in diffs
+merge_request: 21573
+author:
+type: fixed