Revert "Update to SnakeYAML 1.21"

This reverts commit 723d754158.

By: md_5 <git@md-5.net>

paper-api/pom.xml

@@ -73,7 +73,7 @@
         <dependency>
             <groupId>org.yaml</groupId>
             <artifactId>snakeyaml</artifactId>
-            <version>1.21</version>
+            <version>1.19</version>
             <scope>compile</scope>
         </dependency>
         <!-- testing -->
@@ -150,8 +150,8 @@
                         <configuration>
                             <signature>
                                 <groupId>org.codehaus.mojo.signature</groupId>
-                                <artifactId>java17</artifactId>
-                                <version>1.0</version>
+                                <artifactId>java16</artifactId>
+                                <version>1.1</version>
                             </signature>
                         </configuration>
                     </plugin>