Fixed typo in method name in the transactions API demo.
Fixed typo in method name in the transactions API demo.

aslafy-z/mangopay2-php-sdk,andufratu/mangopay2-php-sdk,Mangopay/mangopay2-php-sdk,aslafy-z/mangopay2-php-sdk,Mangopay/mangopay2-php-sdk,andufratu/mangopay2-php-sdk