Fix typos, noticed by Clang.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@113061 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/src/stdexcept.cpp b/src/stdexcept.cpp
index 5f3ffd7..316dff1 100644
--- a/src/stdexcept.cpp
+++ b/src/stdexcept.cpp
@@ -81,7 +81,7 @@
 
 }
 
-#pragma GCC visiblity pop
+#pragma GCC visibility pop
 
 namespace std  // purposefully not using versioning namespace
 {