[llvm] [NFC] Eliminate top-level "using namespace" from some headers. (PR #102751)

[Nikita Popov via llvm-commits]

================
@@ -12,7 +12,7 @@
 #include "RISCVTargetStreamer.h"
 #include "llvm/MC/MCELFStreamer.h"
 
-using namespace llvm;
+namespace llvm {
----------------
nikic wrote:

There's a `namespace llvm {` below that you should move instead.

https://github.com/llvm/llvm-project/pull/102751