Update referred to #6138 (#6146)

Moved 
[Solidity Tutorial - A Full Course on Ethereum, Blockchain Development, Smart Contracts, and the EVM](https://www.youtube.com/watch?v=ipwxYa-F1uY) - Gregory McCubbin @ freeCodeCamp.org & Dapp University (YouTube)
to courses from tutorials,
Thanks :)

courses/free-courses-en.md

@@ -823,6 +823,7 @@
 
 * [Learn Solidity](https://youtube.com/playlist?list=PL16WqdAj66SCOdL6XIFbke-XQg2GW_Avg) - Will it Scale (Youtube)
 * [MASTER Solidity for Blockchain](https://youtube.com/playlist?list=PLS5SEs8ZftgVnWHv2_mkvJjn5HBOkde3g) - Dapp University (Youtube)
+* [Solidity Tutorial - A Full Course on Ethereum, Blockchain Development, Smart Contracts, and the EVM](https://www.youtube.com/watch?v=ipwxYa-F1uY) - Gregory McCubbin @ freeCodeCamp.org & Dapp University (YouTube)
 
 
 ### Swift