ci: cap pathspec at <1.1 in pyproject.toml

pathspec 1.1.0 (released 2026-04-23) made PathSpec a generic class, which
trips `Missing type arguments for generic type` when mypyc self-compiles
`mypy/modulefinder.py`. Our test-requirements pins 1.0.0 already, but the
`.pkg` build env that runs mypyc uses pyproject.toml constraints and
grabs 1.1.0. Add an upper bound there too.

Author: VaggelisD

pyproject.toml

@@ -7,7 +7,7 @@ requires = [
     # the following is from mypy-requirements.txt/setup.py
     "typing_extensions>=4.6.0",
     "mypy_extensions>=1.0.0",
-    "pathspec>=1.0.0",
+    "pathspec>=1.0.0,<1.1",
     "tomli>=1.1.0; python_version<'3.11'",
     "librt>=0.8.0; platform_python_implementation != 'PyPy'",
     # the following is from build-requirements.txt
@@ -51,7 +51,7 @@ dependencies = [
   # When changing this, also update build-system.requires and mypy-requirements.txt
   "typing_extensions>=4.6.0",
   "mypy_extensions>=1.0.0",
-  "pathspec>=1.0.0",
+  "pathspec>=1.0.0,<1.1",
   "tomli>=1.1.0; python_version<'3.11'",
   "librt>=0.8.0; platform_python_implementation != 'PyPy'",
 ]