[Feature] Removing hardcoded prompt timeout

[antonio-amjr]

Fix: project-chip/certification-tool#1038
Related to: project-chip/certification-tool-backend#356

Description

Removes the redundant timeout=60 / PROMPT_TIMEOUT overrides in the onboarding QR/manual-pairing-code prompts. These duplicated the PromptRequest default with no distinct intent, so they now inherit the new project-configurable prompt timeout
from certification-tool-backend (see that PR).

Changed

• onboarding_script_support.py: dropped PROMPT_TIMEOUT = 60 constant and its use.
• tcdd12/tcdd12.py, tcdd14/tcdd14.py: dropped explicit timeout=60 kwargs.

Test plan

• No behavior change when the owning project has no th_config — same 60s default.
• Covered indirectly by backend's test_python_test_case.py / prompt-support tests.