Update 7-zip msi un-installer instructions
Update 7-zip msi un-installer instructions

The instructions as-are do not actually work. The uninstaller flag takes the windows GUID of the msi product code. And the various ```install_flags``` and ```uninstall_flags``` do NOT need leading, or trailing spaces.

@twangboy can confirm this is a better example (also see salt issue #25778 https://github.com/saltstack/salt/issues/25778)
saltstack/salt,saltstack/salt,saltstack/salt,saltstack/salt,saltstack/salt