Reassign sparc-unknown-none-elf to tier 3

It should never have been moved to tier 2.
It is a new platform and the maintainer has agreed
to do tier 3 maintenance for it, not tier 2.

src/doc/rustc/src/platform-support.md

@@ -176,7 +176,6 @@ target | std | notes
 `thumbv8m.base-none-eabi` | * | Bare ARMv8-M Baseline
 `thumbv8m.main-none-eabi` | * | Bare ARMv8-M Mainline
 `thumbv8m.main-none-eabihf` | * | Bare ARMv8-M Mainline, hardfloat
-[`sparc-unknown-none-elf`](./platform-support/sparc-unknown-none-elf.md) | * | Bare 32-bit SPARC V7+
 `wasm32-unknown-emscripten` | ✓ | WebAssembly via Emscripten
 `wasm32-unknown-unknown` | ✓ | WebAssembly
 `wasm32-wasi` | ✓ | WebAssembly with WASI
@@ -314,6 +313,7 @@ target | std | host | notes
 [`riscv64-linux-android`](platform-support/android.md) |   |   | RISC-V 64-bit Android
 `s390x-unknown-linux-musl` |  |  | S390x Linux (kernel 3.2, MUSL)
 `sparc-unknown-linux-gnu` | ✓ |  | 32-bit SPARC Linux
+[`sparc-unknown-none-elf`](./platform-support/sparc-unknown-none-elf.md) | * | Bare 32-bit SPARC V7+
 [`sparc64-unknown-netbsd`](platform-support/netbsd.md) | ✓ | ✓ | NetBSD/sparc64
 [`sparc64-unknown-openbsd`](platform-support/openbsd.md) | ✓ | ✓ | OpenBSD/sparc64
 `thumbv4t-none-eabi` | * |  | Thumb-mode Bare ARMv4T