Update recaptchalib.php

[fpap]

The constructor is changed from the name of the class to __construct

[franz-josef-kaiser]

@fpap Thanks for your PR! The repo didn't change for 8 😊 years tough and I can see that we are 209 commit behind the upstream repo. Did you take a look and diff both to see if upstream fixed the issues this fork is targeting (hint: I did not yet)? Because in case, we might want to change some more things here like adding access definitions like public if we are already onto it? Opinions?

[fpap]

@franz-josef-kaiser no, I did not compared it... 😬 Surely they already fixed it... I agree on improving as much as possible.

[mre33]

After running into this problem with PHP 8.1, I changed the function name to ReCaptchaa and called it separately. In my main code. This needs to be changed in the library code. It doesn't pass the secret key otherwise.

Instead of calling it as:
$reCaptcha = new ReCaptcha( $secret );

Do this instead:
$reCaptcha = new ReCaptcha;
$reCaptcha->ReCaptchaa( $secret ); // had to change the name of this function in recaptchalib file to work with php 8+