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
```

(cherry picked from commit eb78f80f03)

modules/mono/csharp_script.cpp

@@ -345,7 +345,7 @@ Ref<Script> CSharpLanguage::get_template(const String &p_class_name, const Strin
 							 "}\n";
 
 	// Replaces all spaces in p_class_name with underscores to prevent
-	// erronous C# Script templates from being generated when the object name
+	// invalid C# Script templates from being generated when the object name
 	// has spaces in it.
 	String class_name_no_spaces = p_class_name.replace(" ", "_");
 	String base_class_name = get_base_class_name(p_base_class_name, class_name_no_spaces);