py-pyside: restrict version of dependency on v1.2.2 (#26396)

Restrict @:1.2.2 to older sphinx versions to not fail the build

var/spack/repos/builtin/packages/py-pyside/package.py

@@ -30,6 +30,7 @@ class PyPyside(PythonPackage):
 
     depends_on('py-setuptools', type='build')
     depends_on('py-sphinx',        type=('build', 'run'))
+    depends_on('py-sphinx@:3.5.0', type=('build', 'run'), when='@:1.2.2')
     depends_on('qt@4.5:4.9')
     depends_on('libxml2@2.6.32:')
     depends_on('libxslt@1.1.19:')