Docs: Fix deprecated-blocks example (#10717)

## Description
I changed a small error in the deprecated-blocks documentation

## How has this been tested?
I looked in my Github repo if the markdown file preview was ok

## Types of changes
Typo in documentation

docs/block-api/deprecated-blocks.md

@@ -112,7 +112,7 @@ registerBlockType( 'gutenberg/block-with-deprecated-version', {
 	},
 
 	save: function( props ) {
-		return el( 'div', {}, props.attributes.text );
+		return el( 'div', {}, props.attributes.content );
 	},
 
 	deprecated: [
@@ -153,7 +153,7 @@ registerBlockType( 'gutenberg/block-with-deprecated-version', {
 	},
 
 	save( props ) {
-		return <div>{ props.attributes.text }</div>;
+		return <div>{ props.attributes.content }</div>;
 	},
 
 	deprecated: [