tidy-up: mostly whitespace nits

- delete completed TODO from `./CMakeLists.txt`.
- convert a C++ comment to C89 in `./CMake/CurlTests.c`.
- delete duplicate EOLs from EOF.
- add missing EOL at EOF.
- delete whitespace at EOL (except from expected test results).
- convert tabs to spaces.
- convert CRLF EOLs to LF in GHA yaml.
- text casing fixes in `./CMakeLists.txt`.
- fix a codespell typo in `packages/OS400/initscript.sh`.

Closes #11772

docs/HTTP3.md

@@ -340,7 +340,7 @@ should be either in your PATH or your current directory.
 Create a `Caddyfile` with the following content:
 ~~~
 localhost:7443 {
-	respond "Hello, world! you are using {http.request.proto}"
+  respond "Hello, world! you are using {http.request.proto}"
 }
 ~~~