Remove redundant String.join statement

packages/http-client-java/generator/http-client-generator-core/src/main/java/com/microsoft/typespec/http/client/generator/core/template/ModelTestTemplate.java

@@ -101,7 +101,6 @@ private static String getJavaStringExpression(String jsonStr) {
             // avoid "constant string too long"
             StringBuilder sb = new StringBuilder("String.join(\"\"");
             String remains = jsonStr;
-            String.join("", "", "");
             while (remains.length() >= maxConstantStringLength) {
                 String current = remains.substring(0, maxConstantStringLength - 1);
                 remains = remains.substring(maxConstantStringLength - 1);