🩹 Suppress the template_not_found_message when rendering cached blocks on ACF v6.3.x

[Log1x]

A useless "The render template for this ACF Block was not found" message was added in the acf_block_render_template hook when a template file isn't found at some point in ACF Pro 6.3.x.

This hook still makes sense over using a render callback for ACF Composer's use-case despite us echoing the rendered output ourselves so the best workaround is emptying the message using the acf/blocks/template_not_found_message filter when a cached block goes to render.