CI: correct the pkgconf_requirements name

Author: andyfaff

tools/wheels/cibw_before_build.sh

@@ -63,5 +63,5 @@ if [[ $RUNNER_OS == "Windows" ]]; then
     python -m pip install -r $PROJECT_DIR/requirements/delvewheel_requirements.txt
     # pkgconf - carries out the role of pkg-config.
     # Alternative is pkgconfiglite that you have to install with choco
-    python -m pip install -r $PROJECT_DIR/requirements/pkgconf.txt
+    python -m pip install -r $PROJECT_DIR/requirements/pkgconf_requirements.txt
 fi