[fix] [build] rename schema_example.conf to schema_example.json (apac…

…he#21447)

### Motivation

Since the files will be checked for `LICENSE` whose name is a suffix with `.conf`. But we can not add a LICENSE definition for the file `schema_example.conf` because it is a `JSON` file.

Note: the file `schema_example.conf` is only used for the integration test `CLITest.java`.

### Modifications

Rename `schema_example.conf` to `schema_example.json`.

pom.xml

@@ -1683,7 +1683,7 @@ flexible messaging model and an intuitive client API.</description>
                 <exclude>**/ByteBufCodedOutputStream.java</exclude>
                 <exclude>**/ahc.properties</exclude>
                 <exclude>bin/proto/*</exclude>
-                <exclude>conf/schema_example.conf</exclude>
+                <exclude>conf/schema_example.json</exclude>
                 <exclude>data/**</exclude>
                 <exclude>logs/**</exclude>
                 <exclude>**/circe/**</exclude>
@@ -1808,7 +1808,7 @@ flexible messaging model and an intuitive client API.</description>
             <exclude>**/requirements.txt</exclude>
 
             <!-- Configuration Templates -->
-            <exclude>conf/schema_example.conf</exclude>
+            <exclude>conf/schema_example.json</exclude>
             <exclude>**/templates/*.tpl</exclude>
 
             <!-- helm files -->

tests/integration/src/test/java/org/apache/pulsar/tests/integration/cli/CLITest.java

@@ -402,7 +402,7 @@ public void testSchemaCLI() throws Exception {
             "upload",
             topicName,
             "-f",
-            "/pulsar/conf/schema_example.conf"
+            "/pulsar/conf/schema_example.json"
         );
         result.assertNoOutput();