Add FlyingRC F4Wing Mini target updates

[FlyingRC-Official]

Summary

• Rename FLYINGRCF4WINGMINI_NOT_RECOMMENDED to FLYINGRCF4WINGMINI and update the USB product string/docs title.
• Add BMI270 gyro support and correct the default gyro orientation.
• Add the V4 hardware current-sensor ADC pad using PC5 / ADC_CHN_2, matching the Matek F405 TE mapping.
• Polish the board documentation wording and spelling while keeping the hardware limitations clear.

Verification

• git diff --check upstream/maintenance-9.x...HEAD
• Local comparison against iNavFlight/inav:maintenance-9.x shows the PR delta is limited to the FlyingRC F4Wing Mini target and documentation.

Local CMake configure/build was not run because cmake is not installed in this environment.

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[sensei-hacker]

It's good to see you here, @FlyingRC-Official !
By communicating about the different and working together, I think we can make a much better experience for users.
I have also replied to you on the Discord.

[github-actions]

Test firmware build ready — commit 92de3ec

Download firmware for PR #11588

238 targets built. Find your board's .hex file by name on that page (e.g. MATEKF405SE.hex). Files are individually downloadable — no GitHub login required.

Development build for testing only. Use Full Chip Erase when flashing.