gc: fix arg name, mark positional-only args (#3760)

stdlib/3/gc.pyi

@@ -12,7 +12,7 @@ DEBUG_UNCOLLECTABLE: int
 callbacks: List[Any]
 garbage: List[Any]
 
-def collect(generations: int = ...) -> int: ...
+def collect(generation: int = ...) -> int: ...
 def disable() -> None: ...
 def enable() -> None: ...
 def get_count() -> Tuple[int, int, int]: ...
@@ -25,8 +25,8 @@ def get_referents(*objs: Any) -> List[Any]: ...
 def get_referrers(*objs: Any) -> List[Any]: ...
 def get_stats() -> List[Dict[str, Any]]: ...
 def get_threshold() -> Tuple[int, int, int]: ...
-def is_tracked(obj: Any) -> bool: ...
+def is_tracked(__obj: Any) -> bool: ...
 def isenabled() -> bool: ...
-def set_debug(flags: int) -> None: ...
+def set_debug(__flags: int) -> None: ...
 def set_threshold(threshold0: int, threshold1: int = ...,
                   threshold2: int = ...) -> None: ...

tests/stubtest_whitelists/py37.txt

@@ -45,7 +45,6 @@ email.message.MIMEPart.as_string
 email.mime.message.MIMEMessage.__init__
 email.mime.text.MIMEText.__init__
 enum.Enum._generate_next_value_
-gc.collect
 gettext.NullTranslations.npgettext
 gettext.NullTranslations.pgettext
 gettext.dnpgettext

tests/stubtest_whitelists/py38.txt

@@ -114,9 +114,6 @@ fcntl.flock
 fcntl.ioctl
 fcntl.lockf
 functools.partialmethod.__get__
-gc.collect
-gc.is_tracked
-gc.set_debug
 gettext.install
 gettext.translation
 hmac.compare_digest