minor: use extractor's default project to be .yml

Author: piyush kumar sadangi

extractor/src/main/java/com/example/extractor/CheckstyleExampleExtractor.java

@@ -170,7 +170,7 @@ public static void main(final String[] args) throws Exception {
      */
     public static void outputDefaultProjectsList(final String outputPath) {
         try (InputStream inputStream = CheckstyleExampleExtractor.class
-                .getResourceAsStream("/list-of-projects.properties");
+                .getResourceAsStream("/list-of-projects.yml");
              OutputStream outputStream = Files.newOutputStream(Path.of(outputPath))) {
 
             final byte[] buffer = new byte[BUFFER_SIZE];

extractor/src/test/java/com/example/extractor/MainsLauncherTest.java

@@ -54,7 +54,7 @@ class MainsLauncherTest {
     /**
      * The constant for default projects file.
      */
-    private static final String DEFAULT_PROJECTS_FILE = "list-of-projects.properties";
+    private static final String DEFAULT_PROJECTS_FILE = "list-of-projects.yml";
 
     /**
      * Tests the main method of CheckstyleExampleExtractor.