[libc++/abi/unwind] Rename Lit features for no exceptions to 'no-exceptions'

Instead of having different names for the same Lit feature accross code
bases, use the same name everywhere. This NFC commit is in preparation
for a refactor where all three projects will be using the same Lit
feature detection logic, and hence it won't be convenient to use
different names for the feature.

Differential Revision: https://reviews.llvm.org/D78370
diff --git a/libcxx/test/std/re/re.alg/re.alg.replace/exponential.pass.cpp b/libcxx/test/std/re/re.alg/re.alg.replace/exponential.pass.cpp
index 868c3d8..316759f 100644
--- a/libcxx/test/std/re/re.alg/re.alg.replace/exponential.pass.cpp
+++ b/libcxx/test/std/re/re.alg/re.alg.replace/exponential.pass.cpp
@@ -7,7 +7,7 @@
 //===----------------------------------------------------------------------===//
 
 // <regex>
-// UNSUPPORTED: libcpp-no-exceptions
+// UNSUPPORTED: no-exceptions
 
 // template <class OutputIterator, class BidirectionalIterator,
 //           class traits, class charT, class ST, class SA>