subset: explicitly subset ClipList, avoids warning when lazy-loading

relying on ClipList.compile to drop unused clips based on updated glyphOrder won't work when font is loaded lazily (default for subsetter), because ClipList gets decompiled too late (after glyphOrder has already been modified) and this produces warnings about missing glyphIDs.
Better to make the subsetter explicilty prune unused clips.

Lib/fontTools/subset/__init__.py

@@ -2089,6 +2089,9 @@ def subset_glyphs(self, s):
 	)
 	del self.ColorLayersV1
 
+	clips = self.table.ClipList.clips
+	self.table.ClipList.clips = {g: clips[g] for g in clips if g in s.glyphs}
+
 	layersV0 = self.ColorLayers
 	if not self.table.BaseGlyphList.BaseGlyphPaintRecord:
 		# no more COLRv1 glyphs: downgrade to version 0

Tests/subset/subset_test.py

@@ -1092,6 +1092,12 @@ def colrv1_path(tmp_path):
                 ("glyph00018", 2),
             ],
         },
+        clipBoxes={
+            "uniE000": (0, 0, 200, 300),
+            "uniE001": (0, 0, 500, 500),
+            "uniE002": (100, 100, 400, 400),
+            "uniE003": (-50, -50, 350, 350),
+        },
     )
     fb.setupCPAL(
         [
@@ -1171,6 +1177,9 @@ def test_subset_COLRv1_and_CPAL(colrv1_path):
     assert layersV0[1].PaletteIndex == 0xFFFF
     assert layersV0[2].PaletteIndex == 1
 
+    clipBoxes = colr.ClipList.clips
+    assert {"uniE001", "uniE002", "uniE003"} == set(clipBoxes)
+
     assert "CPAL" in subset_font
     cpal = subset_font["CPAL"]
     assert [