Fix typos with codespell

Using codespell 2.1.0.

Method:
```
$ cat > ../godot-word-whitelist.txt << EOF
ang
ans
ba
curvelinear
dof
doubleclick
fave
findn
gird
inout
leapyear
lod
merchantibility
nd
numer
ois
ony
que
readded
seeked
statics

1 files changed, 1 insertions, 1 deletions

diff --git a/core/math/octree.h b/core/math/octree.h
index 7861c35e07..23ba4c1aa3 100644
--- a/core/math/octree.h
+++ b/core/math/octree.h
@@ -103,7 +103,7 @@ private:
 		Octant *parent = nullptr;
 		Octant *children[8] = { nullptr };
 
-		int children_count = 0; // cache for amount of childrens (fast check for removal)
+		int children_count = 0; // cache for amount of children (fast check for removal)
 		int parent_index = -1; // cache for parent index (fast check for removal)
 
 		List<Element *, AL> pairable_elements;