Documentation: RISC-V: Fix a typo in patch-acceptance

I just stumbled on this when modifying the docs.

Reviewed-by: Anup Patel <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Palmer Dabbelt <[email protected]>

Documentation/riscv/patch-acceptance.rst

@@ -29,7 +29,7 @@ their own custom extensions.  These custom extensions aren't required
 to go through any review or ratification process by the RISC-V
 Foundation.  To avoid the maintenance complexity and potential
 performance impact of adding kernel code for implementor-specific
-RISC-V extensions, we'll only to accept patches for extensions that
+RISC-V extensions, we'll only accept patches for extensions that
 have been officially frozen or ratified by the RISC-V Foundation.
 (Implementors, may, of course, maintain their own Linux kernel trees
 containing code for any custom extensions that they wish.)