Constrain to pytket 1.x. (#570)

Author: cqc-alec

setup.py

@@ -45,7 +45,7 @@
     packages=find_namespace_packages(include=["pytket.*"]),
     include_package_data=True,
     install_requires=[
-        "pytket >= 1.39.0",
+        "pytket >= 1.39.0, < 2",
         "pytket-qir >= 0.17, < 0.20",
         "requests >= 2.32.2",
         "types-requests",