fixed php lint issues

src/StringTagField.php

@@ -368,5 +368,4 @@ class StringTagField extends DropdownField
 
         return $this;
     }
-    
 }

tests/TagFieldTest.php

@@ -355,6 +355,5 @@ class TagFieldTest extends SapphireTest
         $field = new TagField('Tags', '', TagFieldTestBlogTag::get());
         $readOnlyField = $field->performReadonlyTransformation();
         $this->assertEquals(ReadonlyTagField::class, get_class($readOnlyField));
-
     }
 }