[bug] Relax dependent Pillow version (#6170)

Fixes #6032

### Brief Summary
see issue above

python/taichi/lang/_texture.py

@@ -161,7 +161,8 @@ def from_image(self, image):
         assert self.num_dims == 2
         assert self.dtype == u8
         assert self.num_channels == 4
-        image = image.transpose(Image.Transpose.ROTATE_90)
+        # Don't use transpose method since its enums are too new
+        image = image.rotate(90, expand=True)
         arr = np.asarray(image)
         from taichi._kernels import \
             load_texture_from_numpy  # pylint: disable=import-outside-toplevel
@@ -181,4 +182,4 @@ def to_image(self):
         from taichi._kernels import \
             save_texture_to_numpy  # pylint: disable=import-outside-toplevel
         save_texture_to_numpy(self, res)
-        return Image.fromarray(res).transpose(Image.TRANSPOSE.ROTATE_270)
+        return Image.fromarray(res).rotate(270, expand=True)

requirements_test.txt

@@ -1,4 +1,4 @@
-Pillow>=9.1.0
+Pillow
 pytest
 pytest-xdist
 pytest-rerunfailures