Fix test expectations on nightly

Apparently the cron stopped running when we renamed `master` -> `main`,
so we missed that these started failing - oops!

num_enum/tests/try_build/compile_fail/conflicting_derive.stderr_nightly

@@ -7,7 +7,7 @@ error[E0119]: conflicting implementations of trait `std::convert::TryFrom<u8>` f
   = note: conflicting implementation in crate `core`:
           - impl<T, U> TryFrom<U> for T
             where U: Into<T>;
-  = note: this error originates in a derive macro (in Nightly builds, run with -Z macro-backtrace for more info)
+  = note: this error originates in the derive macro `num_enum::TryFromPrimitive` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error[E0119]: conflicting implementations of trait `num_enum::TryFromPrimitive` for type `Numbers`
  --> $DIR/conflicting_derive.rs:1:35
@@ -17,4 +17,4 @@ error[E0119]: conflicting implementations of trait `num_enum::TryFromPrimitive`
   |          |
   |          first implementation here
   |
-  = note: this error originates in a derive macro (in Nightly builds, run with -Z macro-backtrace for more info)
+  = note: this error originates in the derive macro `num_enum::TryFromPrimitive` (in Nightly builds, run with -Z macro-backtrace for more info)

num_enum/tests/try_build/compile_fail/exhaustive_enum.stderr_nightly

@@ -0,0 +1,7 @@
+error: #[derive(FromPrimitive)] requires a variant marked with `#[num_enum(default)]`
+ --> $DIR/exhaustive_enum.rs:1:10
+  |
+1 | #[derive(num_enum::FromPrimitive)]
+  |          ^^^^^^^^^^^^^^^^^^^^^^^
+  |
+  = note: this error originates in the derive macro `num_enum::FromPrimitive` (in Nightly builds, run with -Z macro-backtrace for more info)

num_enum/tests/try_build/compile_fail/missing_default.stderr_nightly

@@ -0,0 +1,7 @@
+error: #[derive(FromPrimitive)] requires a variant marked with `#[num_enum(default)]`
+ --> $DIR/missing_default.rs:1:10
+  |
+1 | #[derive(num_enum::FromPrimitive)]
+  |          ^^^^^^^^^^^^^^^^^^^^^^^
+  |
+  = note: this error originates in the derive macro `num_enum::FromPrimitive` (in Nightly builds, run with -Z macro-backtrace for more info)

num_enum/tests/try_build/compile_fail/missing_repr.stderr_nightly

@@ -0,0 +1,7 @@
+error: Missing `#[repr({Integer})]` attribute
+ --> $DIR/missing_repr.rs:1:10
+  |
+1 | #[derive(num_enum::IntoPrimitive)]
+  |          ^^^^^^^^^^^^^^^^^^^^^^^
+  |
+  = note: this error originates in the derive macro `num_enum::IntoPrimitive` (in Nightly builds, run with -Z macro-backtrace for more info)

num_enum/tests/try_build/compile_fail/unreachable_patterns.stderr_nightly

@@ -0,0 +1,12 @@
+error: unreachable pattern
+ --> $DIR/unreachable_patterns.rs:7:5
+  |
+7 |     Two = 2,
+  |     ^^^
+  |
+note: the lint level is defined here
+ --> $DIR/unreachable_patterns.rs:1:10
+  |
+1 | #[derive(num_enum::TryFromPrimitive)]
+  |          ^^^^^^^^^^^^^^^^^^^^^^^^^^
+  = note: this error originates in the derive macro `num_enum::TryFromPrimitive` (in Nightly builds, run with -Z macro-backtrace for more info)