Bump toolchains/riscv-tools/riscv-openocd from bc68bd7 to f51900b

Bumps [toolchains/riscv-tools/riscv-openocd](https://github.com/riscv/riscv-openocd) from `bc68bd7` to `f51900b`.
- [Release notes](https://github.com/riscv/riscv-openocd/releases)
- [Commits](riscv-collab/riscv-openocd@bc68bd7...f51900b)

---
updated-dependencies:
- dependency-name: toolchains/riscv-tools/riscv-openocd
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>