psi4: fix "filter_compilers" signature (#17375)

var/spack/repos/builtin/packages/psi4/package.py

@@ -51,7 +51,7 @@ def cmake_args(self):
         ]
 
     @run_after('install')
-    def filter_compilers(self, spec, prefix):
+    def filter_compilers(self):
         """Run after install to tell the configuration files to
         use the compilers that Spack built the package with.
 
@@ -59,6 +59,9 @@ def filter_compilers(self, spec, prefix):
         Spack's generic cxx. We want it to be bound to
         whatever compiler it was built with."""
 
+        spec = self.spec
+        prefix = spec.prefix
+
         kwargs = {'ignore_absent': True, 'backup': False, 'string': True}
 
         cc_files = ['bin/psi4-config']