fix(embeddings): change default output_type from np to pt in positional embedding helpers

[AloysJehwin]

What does this PR do?

Fixes #14366

Four public helpers in embeddings.py defaulted to output_type='np', which routes into a deprecate() call with target 0.33.0/0.34.0. Since the current version is 0.40.0, deprecate() raises a ValueError before doing anything — so calling these functions with no arguments crashes.

Changed the default to output_type='pt' in:

• get_3d_sincos_pos_embed
• get_2d_sincos_pos_embed
• get_2d_sincos_pos_embed_from_grid
• get_1d_sincos_pos_embed_from_grid
• get_2d_rotary_pos_embed

The deprecated 'np' path is preserved for callers who pass it explicitly.

All eight in-tree call sites already pass output_type='pt' explicitly — this only affects external callers using the default.

Before

from diffusers.models import embeddings as E
E.get_2d_sincos_pos_embed(embed_dim=8, grid_size=2)
# ValueError: The deprecation tuple (..., '0.33.0', ...) should be removed since diffusers' version 0.40.0 is >= 0.33.0

After

E.get_2d_sincos_pos_embed(embed_dim=8, grid_size=2)
# torch.Size([4, 8])  ← works

Implemented with Claude Code assistance. All changed lines reviewed manually.

[AloysJehwin]

Fair point — I went with the minimal change (flip the default) without considering that the intent may be full removal of the np path. Happy to update the PR to remove the deprecated branch entirely if that's the preferred direction, or close and wait for a maintainer to confirm the intended approach. Let me know.