vcbuild: fix batch file name in README

Signed-off-by: NOrgad Shaneh <orgads@gmail.com>
Acked-by: NJohannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

compat/vcbuild/README

@@ -26,8 +26,8 @@ The Steps to Build Git with VS2015 or VS2017 from the command line.
    Use ONE of the following forms which should match how you want to
    compile git.exe.
 
-   $ ./compat/vcbuild/vcpkg_copy_packages.bat debug
-   $ ./compat/vcbuild/vcpkg_copy_packages.bat release
+   $ ./compat/vcbuild/vcpkg_copy_dlls.bat debug
+   $ ./compat/vcbuild/vcpkg_copy_dlls.bat release
 
 3. Build git using MSVC from an SDK bash window using one of the
    following commands: