Fix error in dynamic_mode documentation

[limdor]

auto does not exist in Bazel 4, 5, 6 or 7. I'm not sure if was there before but in any of these versions when trying it the following error appears

ERROR: While parsing option --dynamic_mode=auto: Not a valid dynamic mode: 'auto' (should be off, default or fully)

Fixes: https://github.com/bazelbuild/bazel/issues/20707

[sgowroji]

Hi @fweikert, Since i can see that this PR has been approved, Please let me know whether i should proceed with importing it. Thanks!

[limdor]

Gently reminder. It would be nice to have the documentation updated.

[limdor]

@sgowroji @fweikert can we do something about this PR please? Thanks