docker: Only match tags that start with v* (#120670)
To avoid issues where version could be confused with a ciflow tag.
Example:
```
❯ git describe --tags --always
ciflow/periodic/c3496d50f0bb437c70f27085f71155209277bfd4-47-g4ca24959d1a
❯ git describe --tags --always --match "v[1-9]*.*"
v1.8.0-rc1-36500-g4ca24959d1a
```
Resolves https://github.com/pytorch/pytorch/issues/120392
Signed-off-by: Eli Uriegas <eliuriegas@meta.com>
Pull Request resolved: https://github.com/pytorch/pytorch/pull/120670
Approved by: https://github.com/kit1980, https://github.com/atalman
