Issue #1978112 by andypost: Convert taxonomy admin path to follow other core.

.../field_ui/lib/Drupal/field_ui/Tests/ManageDisplayTest.php

...s/field_ui/lib/Drupal/field_ui/Tests/ManageFieldsTest.php

core/modules/forum/lib/Drupal/forum/Tests/ForumTest.php

...dules/path/lib/Drupal/path/Tests/PathTaxonomyTermTest.php

...es/system/lib/Drupal/system/Tests/Menu/BreadcrumbTest.php

.../taxonomy/lib/Drupal/taxonomy/Plugin/Core/Entity/Term.php

...omy/lib/Drupal/taxonomy/Plugin/Core/Entity/Vocabulary.php

.../modules/taxonomy/lib/Drupal/taxonomy/Tests/HooksTest.php

...s/taxonomy/lib/Drupal/taxonomy/Tests/TermLanguageTest.php

core/modules/taxonomy/lib/Drupal/taxonomy/Tests/TermTest.php

...onomy/lib/Drupal/taxonomy/Tests/TermTranslationUITest.php

.../modules/taxonomy/lib/Drupal/taxonomy/Tests/ThemeTest.php

...nomy/lib/Drupal/taxonomy/Tests/VocabularyLanguageTest.php

...y/lib/Drupal/taxonomy/Tests/VocabularyPermissionsTest.php

...les/taxonomy/lib/Drupal/taxonomy/Tests/VocabularyTest.php

...taxonomy/lib/Drupal/taxonomy/VocabularyFormController.php

core/modules/taxonomy/taxonomy.admin.inc

core/modules/taxonomy/taxonomy.module