Remove redundant at literal in docs (#427)

No need to put literals since it's already in the code section.

cloud-services/src/main/java/cloud/commandframework/services/ServicePipeline.java

@@ -95,8 +95,8 @@ public final class ServicePipeline {
      * <p>
      * The methods should be of the form:
      * <pre>{@code
-     * {@literal @}Nullable
-     * {@literal @}ServiceImplementation(YourService.class)
+     * @Nullable
+     * @ServiceImplementation(YourService.class)
      * public YourResult handle(YourContext) {
      *      return result;
      * }

cloud-services/src/main/java/cloud/commandframework/services/annotations/ServiceImplementation.java

@@ -33,8 +33,8 @@ import java.lang.annotation.Target;
  * Used to bind methods to services, like such:
  *
  * <pre>{@code
- * {@literal @}Nullable
- * {@literal @}ServiceImplementation(YourService.class)
+ * @Nullable
+ * @ServiceImplementation(YourService.class)
  * public YourResult handle(YourContext) {
  *      return result;
  * }