Fix type annotation syntax in MotionEncoder_tc __init__ (comfyanonymous#10186)

## Summary
Fixed incorrect type hint syntax in `MotionEncoder_tc.__init__()` parameter list.

## Changes
- Line 647: Changed `num_heads=int` to `num_heads: int` 
- This corrects the parameter annotation from a default value assignment to proper type hint syntax

## Details
The parameter was using assignment syntax (`=`) instead of type annotation syntax (`:`), which would incorrectly set the default value to the `int` class itself rather than annotating the expected type.

Author: Finn-Hecker

comfy/ldm/wan/model.py

@@ -903,7 +903,7 @@ class MotionEncoder_tc(nn.Module):
     def __init__(self,
                  in_dim: int,
                  hidden_dim: int,
-                 num_heads=int,
+                 num_heads: int,
                  need_global=True,
                  dtype=None,
                  device=None,