Merge pull request #3154 from crlf0710/unapprove_rfc2500

Withdraw RFC 2500 approval & use consistent wording.

Author: joshtriplett

text/0809-box-and-in-for-stdlib.md

@@ -3,7 +3,7 @@
 - RFC PR: [rust-lang/rfcs#809](https://github.com/rust-lang/rfcs/pull/809)
 - Rust Issue: [rust-lang/rust#22181](https://github.com/rust-lang/rust/issues/22181)
 
-# This RFC has been **unapproved**
+# This RFC was previously approved, but later **withdrawn**
 
 For details see the [summary comment].
 

text/1228-placement-left-arrow.md

@@ -3,7 +3,7 @@
 - RFC PR: [rust-lang/rfcs#1228](https://github.com/rust-lang/rfcs/pull/1228)
 - Rust Issue: [rust-lang/rust#27779](https://github.com/rust-lang/rust/issues/27779)
 
-# This RFC has been **unapproved**
+# This RFC was previously approved, but later **withdrawn**
 
 For details see the [summary comment].
 

text/2500-needle.md

@@ -3,6 +3,12 @@
 - RFC PR: [rust-lang/rfcs#2500](https://github.com/rust-lang/rfcs/pull/2500)
 - Rust Issue: [rust-lang/rust#56345](https://github.com/rust-lang/rust/issues/56345)
 
+# This RFC was previously approved, but later **withdrawn**
+
+For details see the [summary comment].
+
+[summary comment]: https://github.com/rust-lang/rust/pull/76901#issuecomment-880169952
+
 # Summary
 [summary]: #summary