util-docker: Fix the broken riscv cross-compiler docker

Previously the line
```
RUN git checkout --recurse-submodules 051b9f7ddb7d136777505ea19c70a41926842b96
```

Was causing an error.

Change-Id: Ia13e676f7113c320d4a335b4999c47de415b278b
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/59351
Tested-by: kokoro <noreply+kokoro@google.com>
Maintainer: Jason Lowe-Power <power.jg@gmail.com>
Reviewed-by: Hoa Nguyen <hoanguyen@ucdavis.edu>
1 file changed