[psutil] Correct terminal and niceness return types (#16756)

Author: iamabhisheknag

stubs/psutil/psutil/__init__.pyi

@@ -288,11 +288,16 @@ class Process:
     def username(self) -> str: ...
     def create_time(self) -> float: ...
     def cwd(self) -> str: ...
-    def nice(self, value: int | None = None) -> int: ...
+
+    @overload
+    def nice(self, value: None = None) -> int: ...
+    @overload
+    def nice(self, value: int) -> None: ...
+
     if sys.platform != "win32":
         def uids(self) -> _ntp.puids: ...
         def gids(self) -> _ntp.pgids: ...
-        def terminal(self) -> str: ...
+        def terminal(self) -> str | None: ...
         def num_fds(self) -> int: ...
     if sys.platform != "darwin":
         def io_counters(self) -> _ntp.pio: ...