refactor: use fixture file for Java test instead of embedded code

tests/basic/test_repomap.py

@@ -350,23 +350,7 @@ class TestRepoMapAllLanguages(unittest.TestCase):
             ),
             "java": (
                 "Test.java",
-                """public interface Greeting {
-    String greet(String name);
-}
-
-public class Test implements Greeting {
-    private String prefix = "Hello";
-
-    public String greet(String name) {
-        return prefix + ", " + name + "!";
-    }
-
-    public static void main(String[] args) {
-        Test greeter = new Test();
-        System.out.println(greeter.greet("World"));
-    }
-}
-""",
+                "",  # Now reads from fixture file
                 "Greeting",  # Key symbol to check
             ),
             "javascript": (