(MAINT) Update i18n testing for schema_i18n macro

This change removes the search for translations defined in YAML files from the `dsc_i18n`
test suite to drop false positives for unused translations.

Testing whether a schema uses an undefined translation for a documentation keyword is
redundant, now that the implementation causes schema generation to _panic_ when it
uses an undefined translation key.

Author: michaeltlombardi

dsc/tests/dsc_i18n.tests.ps1

@@ -130,10 +130,6 @@ BeforeDiscovery {
             if (Test-Path -Path $tomlFile) {
                 $this.LoadFile((Get-Item -Path $tomlFile))
             }
-            $yamlFiles = Get-ChildItem -Path $localesFolder | Where-Object Extension -match 'ya?ml'
-            foreach ($yamlFile in $yamlFiles) {
-                $this.LoadFile($yamlFile)
-            }
 
             $this.CheckTranslations($projectFolder)
         }