(#3502) Update tests to disable extra sources

The Test Kitchen environment has both `hermes` and `hermes-all` enabled.
This results in a duplication of the warning message. This disables all
the sources and then enables just the `hermes` source. # Please enter
the commit message for your changes. Lines starting

tests/pester-tests/features/PageSize.Tests.ps1

@@ -34,6 +34,8 @@
         }
     ) {
         BeforeAll {
+            Disable-ChocolateySource
+            Enable-ChocolateySource -Name hermes
             $Output = Invoke-Choco $Command --page-size $ProvidedSize
         }
 
@@ -55,8 +57,6 @@
                 }
             }
             foreach ($message in $ExpectedMessage) {
-                # The output here may contain duplicated line for the warning about non-30 page size.
-                # We have been unable to reproduce this output in any scenario other than in these tests.
                 $Output.Lines | Should -Contain $message -Because $Output.String
             }
         }