If you don’t wish to use HTML5 input types, you can disable this by adding the following code into your theme’s functions.php file:
add_filter( 'wpcf7_support_html5', '__return_false' );
Note that even the most current browsers partially support HTML5. For example, the latest Firefox doesn’t support the date input type (that allows you to choose a date from a calendar user interface) and the number input type (that allows you to input a number value from a spinbox UI) yet — so Firefox provides a general text input field as a fallback instead of a calendar and spinbox UI. This may confuse users because they can’t detect what type of input value this field expects. So, you may feel that it is better to wait for all browsers to support all HTML5 features completely.
But you don’t need to wait! Contact Form 7 offers a better solution. Contact Form 7 is able to provide jQuery UI-based fallback for the date and number input fields. By using this solution, you can provide calendar UI for the date field and spinbox UI for the number field, respectively, even with Firefox or Internet Explorer.
add_filter( 'wpcf7_support_html5_fallback', '__return_true' );