WebUI cr-input: Fix style of slotted paper-button with Shadow DOM v1.

Bug: 898763
Change-Id: Iff586501573beaea6ddf8e6ea9d9e5675f480bc7
Reviewed-on: https://chromium-review.googlesource.com/c/1303403Reviewed-by: Scott Chen <scottchen@chromium.org>
Commit-Queue: Demetrios Papadopoulos <dpapad@chromium.org>
Cr-Commit-Position: refs/heads/master@{#603750}

ui/webui/resources/cr_elements/cr_input/cr_input.html

@@ -40,7 +40,7 @@
 
       /* Margin between <input> and <paper-button> in the 'suffix' slot */
       :host ::slotted(paper-button[slot=suffix]) {
-        margin-inline-start: var(--cr-button-edge-spacing);
+        margin-inline-start: var(--cr-button-edge-spacing) !important;
       }
 
       :host([invalid]) #label {