[V1][Structured Output] Update llguidance (>= 0.7.11) to avoid AttributeError (no StructTag)

[shen-shanshan]

Update llguidance (>= 0.7.11) to avoid AttributeError (no StructTag) .

When I tested tests/v1/entrypoints/llm/test_struct_output_generate.py with llguidance=0.7.10, I get the error shown below:

AttributeError: module 'llguidance' has no attribute 'StructTag'

Then, I find that only llguidance >= 0.7.11 has the StructTag attribute, find more details here.

Thus, I have updated the version of llguidance in requirements/common.txt.

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