Update OpenBLAS git-submodule using dependabot

[termoshtt]

Dependabot is a bot to create a pull request automatically when the external package is updated, i.e. This will create PR like #76 or #85. https://docs.github.com/en/code-security/dependabot/dependabot-version-updates/configuring-dependabot-version-updates

I have tested it on my fork https://github.com/termoshtt/openblas-src/pull/4, however, this does support upgrade to latest commit not to latest tag. https://github.com/dependabot/dependabot-core/issues/1639