Tests: Improve block clear provisional verification

Clicking visual editor is not very reliable because clearing is dependant upon where click occurs. Escape is most reliable for intent of clearing the focused selected block.

test/e2e/integration/002-adding-blocks.js

@@ -13,7 +13,7 @@ describe( 'Adding blocks', () => {
 		// Default block appender is provisional
 		cy.get( lastBlockSelector ).then( ( firstBlock ) => {
 			cy.get( '.editor-default-block-appender' ).click();
-			cy.get( '.edit-post-visual-editor' ).click();
+			cy.focused().type( '{esc}' );
 			cy.get( lastBlockSelector ).should( 'have.text', firstBlock.text() );
 		} );