x/website/_content/blog: typo in alias-names

[meling]

https://go.dev/blog/alias-names#generic-alias-types

In the number 2 of the numbered list:
... declaration of A provides no indication that it is a generic type.

I believe A should be G.

[griesemer]

Thanks! Will fix shortly.

[gopherbot]

Change https://go.dev/cl/619455 mentions this issue: _content/blog: use correct type name in article on generic aliases (typo)