Storefront - Only display post excerpt on archives

functions.php

add_action( 'init', 'jk_customise_storefront' );

function jk_customise_storefront() {
	// Remove the storefromt post content function
	remove_action( 'storefront_loop_post', 'storefront_post_content', 30 );

	// Add our own custom function
	add_action( 'storefront_loop_post', 'jk_custom_storefront_post_content', 30 );
}

function jk_custom_storefront_post_content() {
	?>
	<div class="entry-content" itemprop="articleBody">
		<?php
			if ( has_post_thumbnail() ) {
				the_post_thumbnail( 'full', array( 'itemprop' => 'image' ) );
			}
		?>
		<?php the_excerpt(); ?>
	</div><!-- .entry-content -->
	<?php
}