docs(ref): Remove blog post link

Blog posts are not evergreen documentation.

Author: epage

src/doc/src/reference/build-scripts.md

@@ -258,8 +258,6 @@ identifier, the value should be a string.
 
 ### `cargo::rustc-check-cfg=CHECK_CFG` {#rustc-check-cfg}
 
-*See the announcement [blog post][check-cfg-blog-post] for more a global view of the feature.*
-
 Add to the list of expected config names and values that is used when checking
 the _reachable_ cfg expressions.