Uncaught TypeError: wp.apiFetch is not a function

as @Alvero pointed out in the comments, instead of just supplying wp-api in the block registration, you now need to specify wp-api-fetch.

$index_js="sample-post/index.js";
wp_register_script(
    'sample-post-block-block-editor',
    plugins_url( $index_js, __FILE__ ),
    array(
        'wp-blocks',
        'wp-i18n',
        'wp-element',
        'wp-api-fetch',
    ),
    filemtime( "$dir/$index_js" )
);

Then within your block, you call it using the wp.apiFetch function:

var registerBlockType = wp.blocks.registerBlockType,
    el = wp.element.createElement,
    __ = wp.i18n.__,
    apiFetch = wp.apiFetch;

const postSelections = [];

const allPosts = apiFetch({path: "/wp/v2/featured-post"}).then(fps => {
    postSelections.push({label: "Select a Post", value: 0});
    $.each( fps, function( key, val ) {
        postSelections.push({label: val.title.rendered, value: val.id});
    });
    return postSelections;
});