[BUGFIX] Remove usage of deprecated method extRelPath

Configuration/TCA/tx_typo3roadmap_domain_model_majorversion.php

@@ -19,7 +19,7 @@ return array(
             'endtime'   => 'endtime',
         ),
         'dynamicConfigFile' => \TYPO3\CMS\Core\Utility\ExtensionManagementUtility::extPath('typo3_roadmap') . 'Configuration/TCA/tx_typo3roadmap_domain_model_majorversion.php',
-        'iconfile'          => TYPO3\CMS\Core\Utility\ExtensionManagementUtility::extRelPath('typo3_roadmap') . 'Resources/Public/Icons/tx_typo3roadmap_domain_model_majorversion.gif',
+        'iconfile'          => TYPO3\CMS\Core\Utility\ExtensionManagementUtility::extPath('typo3_roadmap') . 'Resources/Public/Icons/tx_typo3roadmap_domain_model_majorversion.gif',
     ),
     'interface' => array(
         'showRecordFieldList' => 'hidden,starttime,endtime,title,body_text,regular_support,priority_support,extended_support,php_versions'

Configuration/TCA/tx_typo3roadmap_domain_model_minorversion.php

@@ -17,7 +17,7 @@ return array(
             'disabled' => 'hidden',
         ),
         'dynamicConfigFile' => \TYPO3\CMS\Core\Utility\ExtensionManagementUtility::extPath('typo3_roadmap') . 'Configuration/TCA/tx_typo3roadmap_domain_model_minorversion.php',
-        'iconfile'          => TYPO3\CMS\Core\Utility\ExtensionManagementUtility::extRelPath('typo3_roadmap') . 'Resources/Public/Icons/tx_typo3roadmap_domain_model_minorversion.gif',
+        'iconfile'          => TYPO3\CMS\Core\Utility\ExtensionManagementUtility::extPath('typo3_roadmap') . 'Resources/Public/Icons/tx_typo3roadmap_domain_model_minorversion.gif',
     ),
     'interface' => array(
         'showRecordFieldList' => 'hidden,version,link,focus,estimated,released,major_version'

Configuration/TCA/tx_typo3roadmap_domain_model_phpversion.php

@@ -16,7 +16,7 @@ return array(
             'disabled' => 'hidden',
         ),
         'dynamicConfigFile' => \TYPO3\CMS\Core\Utility\ExtensionManagementUtility::extPath('typo3_roadmap') . 'Configuration/TCA/tx_typo3roadmap_domain_model_phpversion.php',
-        'iconfile'          => TYPO3\CMS\Core\Utility\ExtensionManagementUtility::extRelPath('typo3_roadmap') . 'Resources/Public/Icons/tx_typo3roadmap_domain_model_phpversion.gif',
+        'iconfile'          => TYPO3\CMS\Core\Utility\ExtensionManagementUtility::extPath('typo3_roadmap') . 'Resources/Public/Icons/tx_typo3roadmap_domain_model_phpversion.gif',
     ),
     'interface'   => array(
         'showRecordFieldList' => 'hidden,version,active_support,security_support'