Fix error message.

Previously, this code printed out an error message like this

  ld.lld: error: --reproduce: failed to open /foo: cannot open /foo

Apparently "failed to open /foo:" part is redundant.
diff --git a/lld/ELF/Driver.cpp b/lld/ELF/Driver.cpp
index 1da5574..1888edc 100644
--- a/lld/ELF/Driver.cpp
+++ b/lld/ELF/Driver.cpp
@@ -407,8 +407,7 @@
       Tar->append("version.txt", getLLDVersion() + "\n");
       make<std::unique_ptr<TarWriter>>(std::move(*ErrOrWriter));
     } else {
-      error(Twine("--reproduce: failed to open ") + Path + ": " +
-            toString(ErrOrWriter.takeError()));
+      error("--reproduce: " + toString(ErrOrWriter.takeError()));
     }
   }