cmd/fiximports: skip TestDryRun on plan9-arm
cmd/fiximports: skip TestDryRun on plan9-arm

For golang/go#50775.

Change-Id: I229263c840f406926b1f7c91de2400d4a18f3e16
Reviewed-on: https://go-review.googlesource.com/c/tools/+/380495
Trust: Bryan Mills <1c8aad60184261ccede67f5c63a0d2a3bf3c9ff4@google.com>
Reviewed-by: Daniel Martí <29bf28b42a938ace12a5819da4ed4ba03d82f315@mvdan.cc>

golang/tools,golang/tools,golang/tools,golang/tools,golang/tools