More visible way back to editing data samples. (#408)

Grace/Rob and I feel this is very (perhaps too!) visible now so for the
moment not considering the other options.

Author: microbit-matt-hillsdon

lang/ui.en.json

@@ -48,7 +48,7 @@
     "description": "Back button text"
   },
   "back-to-data-samples-action": {
-    "defaultMessage": "Back to data samples",
+    "defaultMessage": "Edit data samples",
     "description": "Back button text"
   },
   "bluetooth-unsupported-advice": {

src/messages/ui.en.json

@@ -100,7 +100,7 @@
   "back-to-data-samples-action": [
     {
       "type": 0,
-      "value": "Back to data samples"
+      "value": "Edit data samples"
     }
   ],
   "bluetooth-unsupported-advice": [

src/pages/TestingModelPage.tsx

@@ -33,13 +33,9 @@ const TestingModelPage = () => {
       toolbarItemsRight={<ProjectToolbarItems />}
       toolbarItemsLeft={
         <Button
-          size="lg"
-          leftIcon={<BackArrow color="white" />}
-          variant="plain"
-          color="white"
+          leftIcon={<BackArrow />}
+          variant="toolbar"
           onClick={navigateToDataSamples}
-          pr={3}
-          pl={3}
         >
           <FormattedMessage id="back-to-data-samples-action" />
         </Button>