do not install zbuff.h

this API is deprecated, for a loong time now,
all related symbols will be removed in a future version (likely v1.5.0)
and the header file `zbuff.h` doesn't compile from `include/` anyway,
because it needs to be positioned one directory below `zstd.h`.

Also removed `cover.h` from `cmake` installer,
as it should have never been part of this list to begin with.

build/cmake/lib/CMakeLists.txt

@@ -152,9 +152,7 @@ endif ()
 # install target
 install(FILES
     "${LIBRARY_DIR}/zstd.h"
-    "${LIBRARY_DIR}/deprecated/zbuff.h"
     "${LIBRARY_DIR}/dictBuilder/zdict.h"
-    "${LIBRARY_DIR}/dictBuilder/cover.h"
     "${LIBRARY_DIR}/common/zstd_errors.h"
     DESTINATION "${CMAKE_INSTALL_INCLUDEDIR}")