sanity: Update minimum gcc version to 10.1

sanity: Update minimum gcc version to 10.1

Since commit 19004950ad56 ("sanity: Check if the C++ toolchain supports
--std=gnu++20") host GCC must support "--std=gnu++20", which became
available in 10.1. This is already reflected in the documentation [1]
but not here.

Update the sanity check on GCC and raise the minimum version to 10.1.
Remove the dead link to www.softwarecollections.org.

[1]: https://git.yoctoproject.org/yocto-docs/commit/?id=0e538c102bfcb7184c76c2401e8cb878168c4434

Cc: Yoann Congal <yoann.congal@smile.fr>
Signed-off-by: Antonin Godard <antonin.godard@bootlin.com>
Signed-off-by: Mathieu Dubois-Briand <mathieu.dubois-briand@bootlin.com>