Remove unnecessary instantiation of StringRef.

SoName's type has changed from StringRef to std::string, so this
code does not make sense anymore.

llvm-svn: 301490
diff --git a/lld/ELF/InputFiles.cpp b/lld/ELF/InputFiles.cpp
index 973a266..b5c3054 100644
--- a/lld/ELF/InputFiles.cpp
+++ b/lld/ELF/InputFiles.cpp
@@ -665,7 +665,7 @@
       uint64_t Val = Dyn.getVal();
       if (Val >= this->StringTable.size())
         fatal(toString(this) + ": invalid DT_SONAME entry");
-      SoName = StringRef(this->StringTable.data() + Val);
+      SoName = this->StringTable.data() + Val;
       return;
     }
   }