[Android][ReEPwdSave] Use paddings over margin to increase touch target

By using paddings instead of margins (and adding a symmetric bottom
padding), the touch target size increases as demanded by mocks).

Screenshot in the bug.

Bug: 1109727
Change-Id: I0cab8af44002fe2c9978ed770e7678d73d87e6e5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2409959Reviewed-by: Ioana Pandele <ioanap@chromium.org>
Commit-Queue: Friedrich [CET] <fhorschig@chromium.org>
Cr-Commit-Position: refs/heads/master@{#806650}

chrome/android/features/keyboard_accessory/internal/java/res/layout/keyboard_accessory_sheet_tab_option_toggle.xml

@@ -11,7 +11,8 @@
     android:layout_height="wrap_content"
     android:paddingStart="@dimen/keyboard_accessory_suggestion_padding"
     android:paddingEnd="6dp"
-    android:layout_marginTop="8dp"
+    android:paddingTop="8dp"
+    android:paddingBottom="8dp"
     android:fillViewport="true"
     android:minHeight="@dimen/keyboard_accessory_suggestion_height"
     android:background="?attr/selectableItemBackground">