Clarify documentation for squeeze_spatial. Use of squeeze_spatial=True with...

Clarify documentation for squeeze_spatial. Use of squeeze_spatial=True with large images results in an error, either at graph build time (if the input image size is known), or at runtime (if not).

Example error message (for the former case):
ValueError: Can not squeeze dim[1], expected a dimension of 1, got 7 for 'InceptionV3/AuxLogits/SpatialSqueeze' (op: 'Squeeze') with input shapes: [1,7,7,1001].
PiperOrigin-RevId: 181075862