ref-manual/yocto-project-supported-features: Set riscv32 maintainers as TBD

This isn't committed to by anyone at this point to mark as TBD.

(From yocto-docs rev: 6b45207c8db40ef416f12348e066601975a0ca36)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

documentation/ref-manual/yocto-project-supported-features.rst

@@ -226,7 +226,7 @@ builder(s):
      - meta-virt
    * - :wikipedia:`RISC-V (32-bit) <RISC-V>`
      - RISC-V architecture testing (32-bit)
-     - Collective effort
+     - TBD
      - qemuriscv32,
        qemuriscv32,
        qemuriscv32-tc