Open upper interval of 'keyring' dependency

The `keyring` dependency is not optional and is required. Unfortunately,
the way it's defined in `pyproject.toml` today prohibits installation of
keyring v24 and above.

Even though it's not recommended to install python CLIs system wide,
let's do not bit that restrictive unless absolutely necessary
(unsupported version).

Fixes: #22

pyproject.toml

@@ -1,6 +1,6 @@
 [tool.poetry]
 name = "httpie-credential-store"
-version = "3.0.0"
+version = "3.1.0"
 description = "HTTPie: one auth to rule them all!"
 authors = ["Ihor Kalnytskyi <[email protected]>"]
 license = "MIT"
@@ -12,7 +12,7 @@ keywords = ["httpie", "credential", "store", "keychain", "plugin", "auth"]
 [tool.poetry.dependencies]
 python = "^3.7"
 httpie = "^3.1"
-keyring = "^23.5"
+keyring = ">= 23.5"
 
 [tool.poetry.dev-dependencies]
 pytest = "^7.1"