cmake: fix warning for passed package name

CMake produces warnings like below:

CMake Warning (dev) at /home/sergeyb/.local/lib/python3.8/site-packages/cmake/data/share/cmake-3.18/Modules/FindPackageHandleStandardArgs.cmake:273 (message):
  The package name passed to `find_package_handle_standard_args` (TARANTOOL)
  does not match the name of the calling package (Tarantool).  This can lead
  to problems in calling code that expects `find_package` result variables
  (e.g., `_FOUND`) to follow a certain pattern.
Call Stack (most recent call first):
  cmake/FindTarantool.cmake:27 (find_package_handle_standard_args)
  CMakeLists.txt:11 (find_package)
This warning is for project developers.  Use -Wno-dev to suppress it.

This patch fixes package name, warning is gone and output
becomes clear and readable.

cmake/FindTarantool.cmake

@@ -24,7 +24,7 @@ if(TARANTOOL_INCLUDE_DIR)
 endif()
 
 include(FindPackageHandleStandardArgs)
-find_package_handle_standard_args(TARANTOOL
+find_package_handle_standard_args(Tarantool
     REQUIRED_VARS TARANTOOL_INCLUDE_DIR VERSION_VAR TARANTOOL_VERSION)
 if(TARANTOOL_FOUND)
     set(TARANTOOL_INCLUDE_DIRS "${TARANTOOL_INCLUDE_DIR}"