Fix typos with codespell

Using codespell 2.0.0.

Method:
```
$ cat > ../godot-word-whitelist.txt << EOF
ang
curvelinear
dof
doubleclick
fave
findn
GIRD
leapyear
lod
merchantibility
nd
numer
ois
ony
que
seeked
synching
te
uint
unselect
webp
EOF

$ codespell -w -q 3 -I ../godot-word-whitelist.txt --skip="./thirdparty,*.po"
$ git diff // undo unwanted changes
```

modules/fbx/data/fbx_mesh_data.h

@@ -156,7 +156,7 @@ private:
 	/// [0, 2, 1, 3, 4]
 	/// The negative values are computed using this formula: `(-value) - 1`
 	///
-	/// Returns the vertex index from the poligon vertex.
+	/// Returns the vertex index from the polygon vertex.
 	/// Returns -1 if `p_index` is invalid.
 	int get_vertex_from_polygon_vertex(const std::vector<int> &p_face_indices, int p_index) const;