README: Remove comment about boolin toolchains being 64-bit only

As of January 2025 they have riscv32-ilp32d and riscv64-lp64d:

 https://toolchains.bootlin.com/releases_riscv32-ilp32d.html
 https://toolchains.bootlin.com/releases_riscv64-lp64d.html

Signed-off-by: Joel Stanley <[email protected]>
Reviewed-by: Anup Patel <[email protected]>

Author: shenki

README.md

@@ -115,9 +115,6 @@ address with appropriate alignment. Bare-metal GNU toolchains (e.g.
 *riscv64-unknown-elf-gcc*) cannot be used. *Clang/LLVM* can still generate PIE
 images if a bare-metal triple is used (e.g. *-target riscv64-unknown-elf*).
 
-Please note that only a 64-bit version of the toolchain is available in
-the Bootlin toolchain repository for now.
-
 In addition to a toolchain, OpenSBI also requires the following packages on
 the host: