pip compile: exclude --upgrade-package when option and value are passed as a single argument (#5033)
This excludes `--upgrade-package` from `compile_command` when value and
option are passed as a single argument. Eg:
```console
--upgrade-package=package
-P=package
-Ppackage
```
I missed this on #5032.
Fixes #5031.
## Test Plan
Tested locally