Update bazel --cpu= docs to remove hardcoded arch strings.
Update bazel --cpu= docs to remove hardcoded arch strings.

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MOS_MIGRATED_REVID=92573465

bazelbuild/bazel-website,bazelbuild/bazel-website,davidzchen/bazel-website,bazelbuild/bazel-website,davidzchen/bazel-website,davidzchen/bazel-website,davidzchen/bazel-website