use channel-relative urls in rustdoc/intra-doc/field.rs

Author: pietroalbini

src/test/rustdoc/intra-doc/field.rs

@@ -1,4 +1,4 @@
-// @has field/index.html '//a[@href="https://doc.rust-lang.org/nightly/core/ops/range/struct.Range.html#structfield.start"]' 'start'
-// @has field/index.html '//a[@href="https://doc.rust-lang.org/nightly/std/io/error/enum.ErrorKind.html#variant.NotFound"]' 'not_found'
+// @has field/index.html '//a[@href="{{channel}}/core/ops/range/struct.Range.html#structfield.start"]' 'start'
+// @has field/index.html '//a[@href="{{channel}}/std/io/error/enum.ErrorKind.html#variant.NotFound"]' 'not_found'
 //! [start][std::ops::Range::start]
 //! [not_found][std::io::ErrorKind::NotFound]