remove unstable book chapter

src/doc/unstable-book/src/language-features/or-patterns.md

@@ -1,36 +0,0 @@
-# `or_patterns`
-
-The tracking issue for this feature is: [#54883]
-
-[#54883]: https://github.com/rust-lang/rust/issues/54883
-
-------------------------
-
-The `or_pattern` language feature allows `|` to be arbitrarily nested within
-a pattern, for example, `Some(A(0) | B(1 | 2))` becomes a valid pattern.
-
-## Examples
-
-```rust,no_run
-#![feature(or_patterns)]
-
-pub enum Foo {
-    Bar,
-    Baz,
-    Quux,
-}
-
-pub fn example(maybe_foo: Option<Foo>) {
-    match maybe_foo {
-        Some(Foo::Bar | Foo::Baz) => {
-            println!("The value contained `Bar` or `Baz`");
-        }
-        Some(_) => {
-            println!("The value did not contain `Bar` or `Baz`");
-        }
-        None => {
-            println!("The value was `None`");
-        }
-    }
-}
-```