Remove invalid #[doc(alias)] from doc-alias search-index test

Author: GuillaumeGomez

src/test/rustdoc-js/doc-alias.rs

@@ -12,11 +12,7 @@ impl Struct {
 }
 
 impl Trait for Struct {
-    // Shouldn't be listed in aliases!
-    #[doc(alias = "ImplTraitItem")]
     type Target = u32;
-    // Shouldn't be listed in aliases!
-    #[doc(alias = "ImplAssociatedConstItem")]
     const AssociatedConst: i32 = 12;
 
     #[doc(alias = "ImplTraitFunction")]