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
```

1 files changed, 1 insertions, 1 deletions

diff --git a/DONORS.md b/DONORS.md
index 70eb8a7e5a..a903a8b38c 100644
--- a/DONORS.md
+++ b/DONORS.md
@@ -7,7 +7,7 @@ support of generous donors.
 The ways to donate to the project, as well as details on how the funds are
 used, are described on [Godot's website](https://godotengine.org/donate).
 
-The following is a list of the current monthly donors, to be have their
+The following is a list of the current monthly donors, who will have their
 generous deed immortalized in the next stable release of Godot Engine.
 
 ## Platinum sponsors