Windows: psxview cleanup

Replaced this series of statements with a single invocation of the `all`
builtin for brevity and conciseness.

Author: dgmcdona

volatility3/framework/plugins/windows/psxview.py

@@ -75,11 +75,8 @@ def _proc_name_to_string(self, proc):
             "string", max_length=proc.ImageFileName.vol.count, errors="replace"
         )
 
-    def _is_valid_proc_name(self, str):
-        for c in str:
-            if not c in self.valid_proc_name_chars:
-                return False
-        return True
+    def _is_valid_proc_name(self, string: str) -> bool:
+        return all(c in self.valid_proc_name_chars for c in string)
 
     def _filter_garbage_procs(
         self, proc_list: Iterable[extensions.EPROCESS]