PDFViewerUpdate: Fix sidenav icon alignment

R=johntlee@chromium.org

Fixed: 1130854
Change-Id: I546c0650bb940ce8a92d4cf2a3ea54a309ba1346
Bug: 1130854
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2423056Reviewed-by: John Lee <johntlee@chromium.org>
Commit-Queue: Rebekah Potter <rbpotter@chromium.org>
Cr-Commit-Position: refs/heads/master@{#809425}

chrome/browser/resources/pdf/elements/viewer-pdf-sidenav.html

@@ -12,7 +12,7 @@
   #icons {
     display: flex;
     flex-direction: column;
-    min-width: 48px;
+    min-width: 64px;
   }
 
   /* These are dummy styles currently - replace with real content. */
@@ -28,7 +28,7 @@
 
   .button-wrapper {
     --button-wrapper-height: 36px;
-    --button-wrapper-margin: 6px;
+    --button-wrapper-margin: 12px;
     --button-wrapper-total-height: calc(
         var(--button-wrapper-height) + var(--button-wrapper-margin));
     align-items: center;