Add -s tcl to openocd command example in Debug Probe HTML documentation

[JeuneseRPi]

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[P33M]

The commands in the HTML docs are sufficient. Appendix C in the PDF guide duplicates instructions on how to build OpenOCD, and omits the installation step which will put the required scripts into the standard search paths that OpenOCD uses. Adding -s tcl only makes sense if the current working directory of the shell is the root directory of the openocd source repo.

We're in the process of removing significant numbers of "type this on the commandline" steps in the guide in favour of one-click installs or properly managed packages. This is just such an example.

[lurch]

@P33M If the HTML docs are correct, and it's the PDF docs that need updating, should we transfer this issue to pico-feedback?