Update the version of Visual Studio required (#9765)

Summary: Pull Request resolved: https://github.com/facebook/rocksdb/pull/9765

Reviewed By: ajkr

Differential Revision: D35220757

Pulled By: jay-zhuang

fbshipit-source-id: b7749aa9bd04e3c3d7757e5e64921ff422600ec0

CMakeLists.txt

@@ -2,7 +2,7 @@
 #     This cmake build is for Windows 64-bit only.
 #
 # Prerequisites:
-#     You must have at least Visual Studio 2015 Update 3. Start the Developer Command Prompt window that is a part of Visual Studio installation.
+#     You must have at least Visual Studio 2019. Start the Developer Command Prompt window that is a part of Visual Studio installation.
 #     Run the build commands from within the Developer Command Prompt window to have paths to the compiler and runtime libraries set.
 #     You must have git.exe in your %PATH% environment variable.
 #