Remove unnecessary newline from error message

I was writing a test that included this error and noticed the spurios
newline that made writing the test more awkward.

Author: arichardson

llvm/lib/MC/TargetRegistry.cpp

@@ -49,9 +49,8 @@ const Target *TargetRegistry::lookupTarget(StringRef ArchName,
     std::string TempError;
     TheTarget = TargetRegistry::lookupTarget(TheTriple.getTriple(), TempError);
     if (!TheTarget) {
-      Error = "unable to get target for '"
-            + TheTriple.getTriple()
-            + "', see --version and --triple.\n";
+      Error = "unable to get target for '" + TheTriple.getTriple() +
+              "', see --version and --triple.";
       return nullptr;
     }
   }