message: Remove unneeded masquerade_as_nightly_cargo.
  This was accidentally missed when it was stabilized.
diff: @@ -65,13 +65,11 @@ fn virtual_no_default_features() {
  .run();
  p.cargo("check --features foo")
  - .masquerade_as_nightly_cargo()
  .with_status(101)
  .with_stderr("[ERROR] none of the selected packages contains these features: foo")
  .run();
  p.cargo("check --features a/dep1,b/f1,b/f2,f2")
  - .masquerade_as_nightly_cargo()
  .with_status(101)
  .with_stderr("[ERROR] none of the selected packages contains these features: b/f2, f2")
  .run();
  @@ -299,19 +297,16 @@ fn feature_default_resolver() {
  .build();
  p.cargo("check --features testt")
  - .masquerade_as_nightly_cargo()
  .with_status(101)
  .with_stderr("[ERROR] Package `a[..]` does not have the feature `testt`")
  .run();
  p.cargo("run --features test")
  - .masquerade_as_nightly_cargo()
  .with_status(0)
  .with_stdout("feature set")
  .run();
  p.cargo("run --features a/test")
  - .masquerade_as_nightly_cargo()
  .with_status(101)
  .with_stderr("[ERROR] package `a[..]` does not have a dependency named `a`")
  .run();
  