vendored libtiff: go back to v4.2.0 for SDL2 branch

.gitmodules

@@ -13,7 +13,7 @@
 [submodule "external/libtiff"]
 	path = external/libtiff
 	url = https://github.com/libsdl-org/libtiff.git
-	branch = v4.5.1-SDL
+	branch = v4.2.0-SDL
 [submodule "external/zlib"]
 	path = external/zlib
 	url = https://github.com/libsdl-org/zlib.git

CMakeLists.txt

@@ -619,8 +619,6 @@ if(SDL2IMAGE_TIF)
     target_compile_definitions(SDL2_image PRIVATE LOAD_TIF)
     if(SDL2IMAGE_TIF_VENDORED)
         message(STATUS "${PROJECT_NAME}: Using vendored libtiff")
-        # tiff-tests variable is used by vendored libtiff
-        set(tiff-tests OFF CACHE BOOL "libtiff: tests" FORCE)
         # jpeg variable is used by vendored libtiff
         set(jpeg OFF CACHE BOOL "libtiff: jpeg option" FORCE)
         # libdeflate variable is used by vendored libtiff