release: update version to "1.4.0" (#309)

Co-authored-by: katsujukou <[email protected]>

Author: github-actions[bot]

pyproject.toml

@@ -1,6 +1,6 @@
 [tool.poetry]
 name = "backend"
-version = "1.3.1"
+version = "1.4.0"
 description = "OQTOPUS Cloud is a project that provides the architecture of cloud quantum computers as an open-source software (OSS). By using it in conjunction with various OSS provided by [@oqtopus-team](https://github.com/oqtopus-team), you can build a cloud quantum computer system."
 authors = ["oqtopus-team <oqtopus-team[at]googlegroups.com>"]
 readme = "README.md"