Extend parfors test timeout for aarch64.
Extend parfors test timeout for aarch64.

This doubles the amount of time available for aarch64 to run the
parfors tests. Timeouts have been seen to occur on public CI.

numba/numba,numba/numba,numba/numba,IntelLabs/numba,IntelLabs/numba,cpcloud/numba,cpcloud/numba,cpcloud/numba,IntelLabs/numba,numba/numba,cpcloud/numba,IntelLabs/numba,numba/numba,cpcloud/numba,IntelLabs/numba