Update doc(include) paths.

Since rust-lang/rust#60938 the path root changed and
these new paths are required to compile on nightly.

Closes #268.

Author: plotskogwq

src/backend/vector/avx2/mod.rs

@@ -19,7 +19,7 @@
 // missing).
 #![cfg_attr(
     all(feature = "nightly", feature = "stage2_build"),
-    doc(include = "../docs/avx2-notes.md")
+    doc(include = "../../docs/avx2-notes.md")
 )]
 
 pub(crate) mod field;

src/backend/vector/ifma/mod.rs

@@ -9,7 +9,7 @@
 
 #![cfg_attr(
     all(feature = "nightly", feature = "stage2_build"),
-    doc(include = "../docs/ifma-notes.md")
+    doc(include = "../../docs/ifma-notes.md")
 )]
 
 pub mod field;

src/backend/vector/mod.rs

@@ -19,7 +19,7 @@
 // missing).
 #![cfg_attr(
     all(feature = "nightly", feature = "stage2_build"),
-    doc(include = "../docs/parallel-formulas.md")
+    doc(include = "../../docs/parallel-formulas.md")
 )]
 
 #[cfg(not(any(target_feature = "avx2", target_feature = "avx512ifma", rustdoc)))]