Make the schema browser section a subheading on table page (#831)

This makes more sense and paves the way for other refactoring in #828.

src/__snapshots__/storyshots.test.js.snap

@@ -2340,12 +2340,6 @@ exports[`Storyshots Schema Viewer Basic 1`] = `
   <div
     class="schema-viewer svelte-i7idum"
   >
-    <h1
-      class="svelte-df8e92"
-    >
-      Schema
-    </h1>
-     
     <div
       class="svelte-ggdpb7"
     >

src/components/SchemaViewer.svelte

@@ -1,8 +1,6 @@
 <script>
   import SchemaNode from "./SchemaNode.svelte";
   import FilterInput from "./FilterInput.svelte";
-  import PageTitle from "./PageTitle.svelte";
-
   import { pageState } from "../state/stores";
 
   export let app;
@@ -50,8 +48,6 @@
 </script>
 
 <div class="schema-viewer">
-  <PageTitle text={"Schema"} />
-
   <FilterInput />
   <div class="schema-browser">
     <p>

src/pages/TableDetail.svelte

@@ -1,6 +1,7 @@
 <script>
   import HelpHoverable from "../components/HelpHoverable.svelte";
   import SchemaViewer from "../components/SchemaViewer.svelte";
+  import SubHeading from "../components/SubHeading.svelte";
   import { getTableData } from "../state/api";
   import { pageTitle } from "../state/stores";
 
@@ -70,6 +71,11 @@
     <a href="https://docs.telemetry.mozilla.org">docs.telemetry.mozilla.org</a>
     .
   </p>
+
+  <SubHeading
+    title={"Schema Browser"}
+    helpText={"Browse and filter the BigQuery schema for this table."}
+  />
   <SchemaViewer app={params.app} nodes={table.bq_schema} />
 {:catch}
   <NotFound pageName={params.appId} itemType="table" />