shtab: require >= 1.8.0

in 1.7.x, zsh completions were still broken, 1.8.0 fixed that.

pyproject.toml

@@ -37,7 +37,7 @@ dependencies = [
   "platformdirs >=3.0.0, <5.0.0; sys_platform == 'darwin'",  # for macOS: breaking changes in 3.0.0.
   "platformdirs >=2.6.0, <5.0.0; sys_platform != 'darwin'",  # for others: 2.6+ works consistently.
   "argon2-cffi",
-  "shtab>=1.7.0",
+  "shtab>=1.8.0",
 ]
 
 [project.optional-dependencies]