Remove broken pacman command for installing packages

This is a regression from d23d6db

During some cleanup, the command

```
pacman pacman --noconfirm --noprogressbar -Sy
```

got modified to:

```
pacman pacman --noconfirm --noprogressbar -S
```

But this isn't a valid command anymore:

```
root@bastelfreak-nb ~ # pacman --noconfirm --noprogressbar -S
error: no targets specified (use -h for help)
root@bastelfreak-nb ~ #
```

The idea was to prevent partial system upgrades while installing new
packages. To do this, the `sync` option was removed from the
installation routine. The correct fix is to remove the command
completely.

Author: bastelfreak

Diff for: lib/puppet/provider/package/pacman.rb

@@ -248,7 +248,6 @@ def install_from_file
              else
                fail _("Source %{source} is not supported by pacman") % { source: source }
              end
-    pacman "--noconfirm", "--noprogressbar", "-S"
     pacman "--noconfirm", "--noprogressbar", "-U", source
   end
 

Diff for: spec/unit/provider/package/pacman_spec.rb

@@ -97,11 +97,6 @@
           it "should install #{source} directly" do
             resource[:source] = source
 
-            expect(executor).to receive(:execute).
-              with(include("-S") & include("--noprogressbar"), no_extra_options).
-              ordered.
-              and_return("")
-
             expect(executor).to receive(:execute).
               with(include("-U") & include(source), no_extra_options).
               ordered.