Change "is plugin uninstalled?" check to always run

Previously the check would only run if the plugin was require-dev.
That behaviour is incorrect, as the check should always be done.
If the plugin is not installed, it doesn't make sense to return an
error under any circumstances.

This commit fixes that oversight.

src/Plugin.php

@@ -185,8 +185,6 @@ public function onDependenciesChangedEvent()
                 $io->write(sprintf('<info>%s</info>', self::MESSAGE_NOTHING_TO_INSTALL));
             }
         } else {
-            $isDev = array_key_exists(self::PLUGIN_NAME, $this->composer->getPackage()->getDevRequires());
-
             $pluginPackage = $this
                 ->composer
                 ->getRepositoryManager()
@@ -196,7 +194,7 @@ public function onDependenciesChangedEvent()
 
             $isPluginUninstalled = count($pluginPackage) === 0;
 
-            if ($isDev && $isPluginUninstalled) {
+            if ($isPluginUninstalled) {
                 if ($isVerbose) {
                     $io->write(sprintf('<info>%s</info>', self::MESSAGE_PLUGIN_UNINSTALLED));
                 }