ReleaseNotes: fix the VS version; follow-up to r297097

llvm-svn: 297203
diff --git a/llvm/docs/ReleaseNotes.rst b/llvm/docs/ReleaseNotes.rst
index f9b0d59..99304a6 100644
--- a/llvm/docs/ReleaseNotes.rst
+++ b/llvm/docs/ReleaseNotes.rst
@@ -31,7 +31,7 @@
 Non-comprehensive list of changes in this release
 =================================================
 * The minimum compiler version required for building LLVM has been raised to
-  4.8 for GCC and 2017 for Visual Studio.
+  4.8 for GCC and 2015 for Visual Studio.
 
 * The C API functions ``LLVMAddFunctionAttr``, ``LLVMGetFunctionAttr``,
   ``LLVMRemoveFunctionAttr``, ``LLVMAddAttribute``, ``LLVMRemoveAttribute``,