Documentation: Remove CONFIG_ARMV7M_USEBASEPRI from code base

[xiaoxiang781216]

Summary

since the basepri is always used without any configuration

Impact

continue clean up from #15073

Testing

ci

[nuttxpr]

[Experimental Bot, please feedback here]

No, this PR does not appear to meet the NuttX requirements based on the provided information. The summary is far too vague. It needs to clearly state what is being changed and why. "since the basepri is always used without any configuration" doesn't tell us anything about the actual change.

The impact section is also insufficient. It references a previous PR but doesn't explain the impact of this PR. All the "NO/YES" questions should be answered explicitly with explanations where necessary.

Finally, "ci" for testing is not acceptable. The requirements ask for specific build host and target information, as well as before/after testing logs. Simply saying "ci" doesn't demonstrate that the changes have been adequately tested. The reviewer needs to see the evidence.

[xiaoxiang781216]

Fix the concern from #15100.

[hartmannathan]

The change is correct. BASEPRI is always used in ARM targets that have it. Thank you!