Remove c_unwind from tests and fix tests

tests/fail/function_calls/exported_symbol_bad_unwind1.rs

@@ -1,5 +1,3 @@
-#![feature(c_unwind)]
-
 #[no_mangle]
 extern "C-unwind" fn unwind() {
  panic!();

tests/fail/function_calls/exported_symbol_bad_unwind2.rs

@@ -4,7 +4,7 @@
 //@normalize-stderr-test: "\n +[0-9]+:[^\n]+" -> ""
 //@normalize-stderr-test: "\n +at [^\n]+" -> ""
 //@[definition,both]error-in-other-file: aborted execution
-#![feature(rustc_attrs, c_unwind)]
+#![feature(rustc_attrs)]
 
 #[cfg_attr(any(definition, both), rustc_nounwind)]
 #[no_mangle]

tests/fail/panic/bad_unwind.rs

@@ -1,5 +1,3 @@
-#![feature(c_unwind)]
-
 //! Unwinding when the caller ABI is "C" (without "-unwind") is UB.
 // The opposite version (callee does not allow unwinding) is impossible to
 // even write: MIR validation catches functions that have `UnwindContinue` but

tests/fail/terminate-terminator.rs

@@ -7,8 +7,6 @@
 // Enable MIR inlining to ensure that `TerminatorKind::UnwindTerminate` is generated
 // instead of just `UnwindAction::Terminate`.
 
-#![feature(c_unwind)]
-
 struct Foo;
 
 impl Drop for Foo {

tests/fail/unwind-action-terminate.rs

@@ -3,8 +3,6 @@
 //@normalize-stderr-test: "\| +\^+" -> "| ^"
 //@normalize-stderr-test: "\n +[0-9]+:[^\n]+" -> ""
 //@normalize-stderr-test: "\n +at [^\n]+" -> ""
-#![feature(c_unwind)]
-
 extern "C" fn panic_abort() {
  panic!()
 }

tests/panic/function_calls/exported_symbol_good_unwind.rs

@@ -2,7 +2,7 @@
 // found in this form" errors works without `-C prefer-dynamic` (`panic!` calls foreign function
 // `__rust_start_panic`).
 // no-prefer-dynamic
-#![feature(c_unwind, unboxed_closures)]
+#![feature(unboxed_closures)]
 
 use std::panic;