7241 Undo creation of constants due to @api reasons

See magento#11462 (review)

Author: avstudnitz

app/code/Magento/Config/Model/Config/Source/Nooptreq.php

@@ -11,19 +11,15 @@
  */
 class Nooptreq implements \Magento\Framework\Option\ArrayInterface
 {
-    const VALUE_NO = '';
-    const VALUE_OPTIONAL = 'opt';
-    const VALUE_REQUIRED = 'req';
-
     /**
      * @return array
      */
     public function toOptionArray()
     {
         return [
-            ['value' => self::VALUE_NO, 'label' => __('No')],
-            ['value' => self::VALUE_OPTIONAL, 'label' => __('Optional')],
-            ['value' => self::VALUE_REQUIRED, 'label' => __('Required')]
+            ['value' => '', 'label' => __('No')],
+            ['value' => 'opt', 'label' => __('Optional')],
+            ['value' => 'req', 'label' => __('Required')]
         ];
     }
 }

app/code/Magento/Customer/Model/Options.php

@@ -45,7 +45,7 @@ public function getNamePrefixOptions($store = null)
     {
         return $this->prepareNamePrefixSuffixOptions(
             $this->addressHelper->getConfig('prefix_options', $store),
-            $this->addressHelper->getConfig('prefix_show', $store) == NooptreqSource::VALUE_OPTIONAL
+            $this->addressHelper->getConfig('prefix_show', $store) == 'opt'
         );
     }
 
@@ -59,7 +59,7 @@ public function getNameSuffixOptions($store = null)
     {
         return $this->prepareNamePrefixSuffixOptions(
             $this->addressHelper->getConfig('suffix_options', $store),
-            $this->addressHelper->getConfig('suffix_show', $store) == NooptreqSource::VALUE_OPTIONAL
+            $this->addressHelper->getConfig('suffix_show', $store) == 'opt'
         );
     }