Fix typos with codespell

Using codespell 1.14.0.

Method:
```
$ cat > ../godot-word-whitelist.txt << EOF
ang
doubleclick
lod
nd
numer
que
te
unselect
EOF
$ codespell -w -q 3 -I ../godot-word-whitelist.txt --skip="./thirdparty,*.po"
$ git diff // undo unwanted changes
```

scene/resources/visual_shader.cpp

@@ -569,7 +569,7 @@ bool VisualShader::_set(const StringName &p_name, const Variant &p_value) {
 		String mode = name.get_slicec('/', 1);
 		int value = p_value;
 		if (value == 0) {
-			modes.erase(mode); //means its default anyway, so dont store it
+			modes.erase(mode); //means it's default anyway, so don't store it
 		} else {
 			modes[mode] = value;
 		}