Fix typos with codespell

Using codespell 1.15.0.

Method:
```
$ cat > ../godot-word-whitelist.txt << EOF
ang
curvelinear
doubleclick
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
```

core/io/http_client.cpp

@@ -429,7 +429,7 @@ Error HTTPClient::poll() {
 					response_num = RESPONSE_OK;
 
 					// Per the HTTP 1.1 spec, keep-alive is the default.
-					// Not following that specification breaks standard implemetations.
+					// Not following that specification breaks standard implementations.
 					// Broken web servers should be fixed.
 					bool keep_alive = true;