Update "gcc" license link

Closes #1772

gcc/license.md

@@ -1 +1 @@
-View [license information](https://gcc.gnu.org/viewcvs/gcc/trunk/gcc/COPYING3?view=markup) for the software contained in this image.
+View [license information](https://gcc.gnu.org/onlinedocs/gcc-11.2.0/gcc/Copying.html) for the software contained in this image.