legacy log_points' positions parameter is now mandatory

This is fine because A) this won't ever be released and B) as [1] shows, nobody as ever used
```
rr.log_points("a/b/c", colors=[red, blue, blue])
```
since that simply never worked.

[1] https://github.com/rerun-io/rerun/blob/main/rerun_py/rerun_sdk/rerun/log/points.py#L225-L226

rerun_py/rerun_sdk/rerun/log/points.py

@@ -24,7 +24,7 @@
 @log_decorator
 def log_point(
     entity_path: str,
-    position: npt.ArrayLike | None = None,
+    position: npt.ArrayLike,
     *,
     radius: float | None = None,
     color: Color | None = None,
@@ -93,6 +93,8 @@ def log_point(
         class_id = 0
     if position is not None:
         position = np.require(position, dtype="float32")
+    else:
+        raise ValueError("`position` argument must be set")
 
     if position is not None:
         if position.size == 2:
@@ -124,7 +126,7 @@ def log_point(
 @log_decorator
 def log_points(
     entity_path: str,
-    positions: npt.ArrayLike | None = None,
+    positions: npt.ArrayLike,
     *,
     identifiers: npt.ArrayLike | None = None,
     colors: Color | Colors | None = None,
@@ -200,7 +202,7 @@ def log_points(
     if keypoint_ids is not None and class_ids is None:
         class_ids = 0
     if positions is None:
-        positions = np.require([], dtype="float32")
+        raise ValueError("`positions` argument must be set")
     else:
         positions = np.require(positions, dtype="float32")