Enable doc upload for tags, disable for release branches (#3153)

Summary:
- Disabled doc upload for branches like release/x.x
- Enabled publishing for tags.

Tested locally:
```
export GITHUB_REF=refs/tags/v3.1.4-rc5
bash test-version.py
```
```
# test-version.py
if [[ "${GITHUB_REF}" =~ ^refs/tags/v([0-9]+\.[0-9]+)\.* ]]; then
  TARGET_FOLDER="${BASH_REMATCH[1]}"
else
  TARGET_FOLDER="main"
fi
echo "Target folder: ${TARGET_FOLDER}"
```
Output:
```
Target folder: 3.1
```
One more:
```
export GITHUB_REF=refs/tags/v1.15.4
bash test-version.sh
```
Output:
```
Target folder: 1.15
```

Pull Request resolved: https://github.com/pytorch/executorch/pull/3153

Reviewed By: dbort

Differential Revision: D56445037

Pulled By: svekars

fbshipit-source-id: e7328523dfe308e8921c1e4f365d9a757d053191