Fix -Wsign-compare in gimpbase/gimpparamspecs.
Hii, I hope this contribution will fix some warning.
../libgimpbase/gimpparamspecs.c: In function ‘gimp_param_object_array_validate’:
../libgimpbase/gimpparamspecs.c:1443:21: warning: comparison of integer expressions of different signedness: ‘gint’ {aka ‘int’} and ‘gsize’ {aka ‘long unsigned int’} [-Wsign-compare]
1443 | for (i = 0; i < array->length; i++)
| ^
../libgimpbase/gimpparamspecs.c: In function ‘gimp_object_array_new’:
../libgimpbase/gimpparamspecs.c:1311:21: warning: comparison of integer expressions of different signedness: ‘gint’ {aka ‘int’} and ‘gsize’ {aka ‘long unsigned int’} [-Wsign-compare]
1311 | for (i = 0; i < length; i++)
| ^
../libgimpbase/gimpparamspecs.c: In function ‘gimp_object_array_free’:
../libgimpbase/gimpparamspecs.c:1356:25: warning: comparison of integer expressions of different signedness: ‘gint’ {aka ‘int’} and ‘gsize’ {aka ‘long unsigned int’} [-Wsign-compare]
1356 | for (i = 0; i < array->length; i++)
| ^