ci: Fix Checkstyle configuration

Update configuration to address the following warning:

```
The Checkstyle rules file could not be parsed. cannot initialize module TreeWalker - TreeWalker is not allowed as a parent of LineLength Please review 'Parent Module' section for this Check in web documentation if Check is standard. The file has been blocked for 60s.
```

config/checkstyle.xml

@@ -27,6 +27,13 @@
     <!--
     <module name="FileLength"/>
     -->
+    <module name="LineLength">
+        <!-- what is a good max value? -->
+        <property name="max" value="120"/>
+        <!-- ignore lines like "$File: //depot/... $" -->
+        <property name="ignorePattern" value="\$File.*\$"/>
+        <property name="severity" value="error"/>
+    </module>
 
     <!-- Checks for whitespace                               -->
     <!-- See http://checkstyle.sf.net/config_whitespace.html -->
@@ -173,13 +180,6 @@
 
         <!-- Checks for Size Violations.                    -->
         <!-- See http://checkstyle.sf.net/config_sizes.html -->
-        <module name="LineLength">
-          <!-- what is a good max value? -->
-          <property name="max" value="120"/>
-          <!-- ignore lines like "$File: //depot/... $" -->
-          <property name="ignorePattern" value="\$File.*\$"/>
-          <property name="severity" value="error"/>
-        </module>
         <module name="MethodLength">
           <property name="tokens" value="METHOD_DEF"/>
           <!-- TODO: We should set this value around 40 or 50 -->