You can use the second parameter of the_post_thumbnail() function.
the_post_thumbnail( 'mudra-featured-image', ['alt' => get_the_title()] );
Another option, you can do this using the filter wp_get_attachment_image_attributes
add_filter('wp_get_attachment_image_attributes', function($attr){
$attr['alt'] = get_the_title();
return $attr;
});
Note, using the filter will affect other images printed using any function that depends on wp_get_attachment_image()
So, you may use the other two attributes passed to the callback function for more control.
Example, if you want apply this only on the size “mudra-featured-image”, your code will be something like this
add_filter( 'wp_get_attachment_image_attributes', function( $attr, $attachment, $size ){
// Return the current $attr array as it is if the size is not "mudra-featured-image"
if( 'mudra-featured-image' !== $size ){
return $attr;
}
// If it is our targeted size then, change the "alt" attribute
$attr['alt'] = get_the_title();
return $attr;
}, 10, 3 );