Upgrade Fluent UI v8 (#688)

Co-authored-by: Steve Faulkner <southpolesteve@gmail.com>

src/Explorer/Controls/Settings/SettingsSubComponents/MongoIndexingPolicy/AddMongoIndexComponent.tsx

@@ -8,7 +8,7 @@ import {
   Dropdown,
   IDropdownOption,
   ITextField,
-} from "office-ui-fabric-react";
+} from "@fluentui/react";
 import {
   addMongoIndexSubElementsTokens,
   mongoErrorMessageStyles,

src/Explorer/Controls/Settings/SettingsSubComponents/MongoIndexingPolicy/MongoIndexingPolicyComponent.tsx

@@ -12,7 +12,7 @@ import {
   Spinner,
   SpinnerSize,
   Separator,
-} from "office-ui-fabric-react";
+} from "@fluentui/react";
 import {
   addMongoIndexStackProps,
   customDetailsListStyles,

src/Explorer/Controls/Settings/SettingsSubComponents/MongoIndexingPolicy/__snapshots__/AddMongoIndexComponent.test.tsx.snap

@@ -30,7 +30,7 @@ exports[`AddMongoIndexComponent renders 1`] = `
       }
       value="sample_key"
     />
-    <StyledWithResponsiveMode
+    <Dropdown
       ariaLabel="Index Type 1"
       onChange={[Function]}
       options={
@@ -67,7 +67,7 @@ exports[`AddMongoIndexComponent renders 1`] = `
       onClick={[Function]}
     />
   </Stack>
-  <StyledMessageBarBase
+  <StyledMessageBar
     messageBarType={1}
     styles={
       Object {
@@ -78,6 +78,6 @@ exports[`AddMongoIndexComponent renders 1`] = `
     }
   >
     sample error
-  </StyledMessageBarBase>
+  </StyledMessageBar>
 </Stack>
 `;