fix title

Signed-off-by: xizheyin <xizheyin@smail.nju.edu.cn>

Author: xizheyin

src/doc/unstable-book/src/language-features/rustc-private.md

@@ -13,7 +13,7 @@ that is necessary for linking against dylibs that statically link `std` (such as
 This makes this feature "viral" in linkage; its use in a given crate makes its use required in
 dependent crates which link to it (including integration tests, which are built as separate crates).
 
-## Required Components
+## Common linker failures related to missing LLVM libraries
 
 ### When using `rustc-private` with Official Toolchains