techdocs: fix double scroll bug

Signed-off-by: Fredrik Adelöw <freben@gmail.com>

.changeset/metal-parents-brush.md

@@ -0,0 +1,5 @@
+---
+'@backstage/plugin-techdocs': patch
+---
+
+Fix double scrollbar bug in reader

plugins/techdocs/src/reader/transformers/styles/rules/layout.ts

@@ -74,6 +74,7 @@ export default ({ theme, sidebar }: RuleOptions) => `
 }
 .md-sidebar .md-sidebar__scrollwrap {
   width: calc(12.1rem);
+  overflow-y: hidden;
 }
 .md-sidebar--secondary {
   right: ${theme.spacing(3)}px;
@@ -234,7 +235,7 @@ export default ({ theme, sidebar }: RuleOptions) => `
   #toggle-sidebar {
     display: none;
   }
-  
+
   .md-content {
     margin: 0;
     width: 100%;