package/gdal: drop remnants of cmake workarounds

In 2b43579e9453 (package/gdal: switch to cmake build to fix libgeotiff
detection) a workaround was added to use the generated 'Makefile' rather
than the bundled-for-autotools GNUMakefile, which was supposedly removed
for the then upcoming 3.6 version.

In 4c17985880be (package/gdal: bump version to 3.6.2) the bump occured,
but the workaround was left untouched. However, in 3.6.2, there is
indeed no GNUMakefile anymore.

Drop the workaround now.

Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>

package/gdal/gdal.mk

@@ -14,13 +14,6 @@ GDAL_INSTALL_STAGING = YES
 GDAL_CONFIG_SCRIPTS = gdal-config
 GDAL_SUPPORTS_IN_SOURCE_BUILD = NO
 
-# Using 'make' with CMake's Makefile generator will not work, as
-# 'make' uses GNUmakefile first, but GNUmakefile is provided by
-# autotools in gdal. We need to force 'make' to use the Makefile,
-# which is generated by CMake. GNUmakefile and autoconf are dropped in
-# 3.6 so this can be dropped in future version.
-GDAL_MAKE_OPTS += -f Makefile
-
 # gdal at its core only needs host-pkgconf, libgeotiff, proj and tiff
 # but since by default mrf driver support is enabled, it also needs
 # jpeg, libpng and zlib. By default there are also many other drivers