Settings WebUI: Fix typo in style include on Search Engines page

Change-Id: I5923a4433bcbfd1a9538d533958b49beb1f17aa2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2210910
Commit-Queue: John Lee <johntlee@chromium.org>
Reviewed-by: dpapad <dpapad@chromium.org>
Cr-Commit-Position: refs/heads/master@{#771265}

chrome/browser/resources/settings/search_engines_page/search_engines_page.html

-    <style include="cr shared-style settings-shared iron-flex">
+    <style include="cr-shared-style settings-shared iron-flex">
       settings-omnibox-extension-entry {
         border-top: var(--cr-separator-line);
       }