Update some tests that now support stable.

Author: ehuss

tests/testsuite/build_script.rs

@@ -2276,11 +2276,6 @@ fn flags_go_into_tests() {
 
 #[cargo_test]
 fn diamond_passes_args_only_once() {
-    // FIXME: when pipelining rides to stable, enable this test on all channels.
-    if !cargo_test_support::is_nightly() {
-        return;
-    }
-
     let p = project()
         .file(
             "Cargo.toml",

tests/testsuite/rustc_info_cache.rs

@@ -4,11 +4,6 @@ use std::env;
 
 #[cargo_test]
 fn rustc_info_cache() {
-    // FIXME: when pipelining rides to stable, enable this test on all channels.
-    if !cargo_test_support::is_nightly() {
-        return;
-    }
-
     let p = project()
         .file("src/main.rs", r#"fn main() { println!("hello"); }"#)
         .build();

tests/testsuite/rustdoc.rs

@@ -1,4 +1,4 @@
-use cargo_test_support::{basic_manifest, is_nightly, project};
+use cargo_test_support::{basic_manifest, project};
 
 #[cargo_test]
 fn rustdoc_simple() {
@@ -163,11 +163,6 @@ fn features() {
 
 #[cargo_test]
 fn proc_macro_crate_type() {
-    // NOTE - Remove this once 'rustdoc --crate-type'
-    // rides to stable
-    if !is_nightly() {
-        return;
-    }
     let p = project()
         .file(
             "Cargo.toml",