Removing sorting option for columns on the post lists page

The filter hook manage_edit-post_sortable_columns contains all the columns, which are sortable. So you could hook into this filter and unset the title:

<?php

add_filter( 'manage_edit-post_sortable_columns', 'wse_240787' );
function wse_240787( $col ) {
    unset( $col['title'] );
    return $col;
}

This filter is documented in wp-admin/includes/class-wp-list-table.php:

  /**
     * Filters the list table sortable columns for a specific screen.
     *
     * The dynamic portion of the hook name, `$this->screen->id`, refers
     * to the ID of the current screen, usually a string.
     *
     * @since 3.5.0
     *
     * @param array $sortable_columns An array of sortable columns.
     */

$_sortable = apply_filters( "manage_{$this->screen->id}_sortable_columns", $sortable_columns );

Since our current screen Id is edit-post the filter is manage_edit-post_sortable_columns.

If you are using a custom post type, the screen ID would change to edit-{$cpt_slug}. For example for pages it would be edit-page. If your CPT is sponsor, it would be edit-sponsor. (Thanks @bravokeyl for pointing to this).