Remove unknown_clippy_lints allow attribute

Author: flip1995

clippy_lints/src/utils/diagnostics.rs

@@ -186,8 +186,6 @@ pub fn span_lint_hir_and_then(
 ///     |
 ///     = note: `-D fold-any` implied by `-D warnings`
 /// ```
-
-#[allow(clippy::unknown_clippy_lints)]
 #[cfg_attr(feature = "internal-lints", allow(clippy::collapsible_span_lint_calls))]
 pub fn span_lint_and_sugg<'a, T: LintContext>(
     cx: &'a T,