fix URLs in doc comment

The angle brackets were confusing my IDE and I thought they were unnecessary. I was wrong.

Author: richkadel

compiler/rustc_middle/src/mir/coverage.rs

@@ -21,9 +21,9 @@ rustc_index::newtype_index! {
 impl ExpressionOperandId {
     /// An expression operand for a "zero counter", as described in the following references:
     ///
-    /// * https://github.com/rust-lang/llvm-project/blob/rustc/11.0-2020-10-12/llvm/docs/CoverageMappingFormat.rst#counter
-    /// * https://github.com/rust-lang/llvm-project/blob/rustc/11.0-2020-10-12/llvm/docs/CoverageMappingFormat.rst#tag
-    /// * https://github.com/rust-lang/llvm-project/blob/rustc/11.0-2020-10-12/llvm/docs/CoverageMappingFormat.rst#counter-expressions
+    /// * <https://github.com/rust-lang/llvm-project/blob/rustc/11.0-2020-10-12/llvm/docs/CoverageMappingFormat.rst#counter>
+    /// * <https://github.com/rust-lang/llvm-project/blob/rustc/11.0-2020-10-12/llvm/docs/CoverageMappingFormat.rst#tag>
+    /// * <https://github.com/rust-lang/llvm-project/blob/rustc/11.0-2020-10-12/llvm/docs/CoverageMappingFormat.rst#counter-expressions>
     ///
     /// This operand can be used to count two or more separate code regions with a single counter,
     /// if they run sequentially with no branches, by injecting the `Counter` in a `BasicBlock` for