fix formatting CIRCLECI_TAG when building docs

[mattip]

Related to pytorch/text#1416. Minor version became two digits which broke the old code, resulting in docs being pushed to the wrong directory

[mthrok]

The upload_docs job is not triggered on release tag (RC or not). (build workflow is not triggered for git tag)

And the build workflow is triggered when a commit is made on release branch, but in this case, there is no tag, because typically tag is pushed separately.

So, to see the effect of this change, first, we need to update the logic around the doc push for release.

I think it should either look into the branch name.

[malfet]

@mthrok this is true, but one can simulate the behavior by doing something like the following:

 % export CIRCLE_TAG=v0.11.3-rc2
 % echo ${CIRCLE_TAG:1:5}
0.11.
 % echo $(echo $CIRCLE_TAG | sed -e 's/v*\([0-9.]*\).*/\1/')
0.11.3