Revert "Remove behavior left behind from a previous iteration"

This reverts commit e51caf2.

Author: epage

text/3857-cfg-version.md

@@ -238,7 +238,9 @@ So given `--check-cfg 'cfg(foo, values(since("1.95.0")))'`,
 A new built-in cfg `--cfg rust=<version>` will be added by the compiler
 that specifies the language version.
 This will be the version of `rustc` with the behavior for pre-release versions being unspecified.
-We expect rustc to strip pre-release versions, treating them as if they fully implement that language version.
+We expect rustc to:
+- Translate the `-nightly` pre-release to `-incomplete
+- Strip the `-beta.5` pre-release
 
 `rust` will be specified as `--check-cfg 'cfg(rust, values(since("1.95.0")))'`
 (or whatever version this gets stabilized in).