Remove -Werror java compiler flag that prevented compilation with openjdk-11

Compiling with openjdk-11 gets the warning "bootstrap class path not set in conjunction with -source 8"
and -Werror causes the compilation to fail.

Author: steinarb

datetime/pom.xml

@@ -103,7 +103,6 @@
             <Xmaxerrs>10000</Xmaxerrs>
             <Xmaxwarns>10000</Xmaxwarns>
             <Xlint />
-            <Werror />
           </compilerArguments>
         </configuration>
       </plugin>

parameter-names/pom.xml

@@ -75,7 +75,6 @@ introspection of method/constructor parameter names, without having to add expli
           <optimize>true</optimize>
           <compilerArgs>
             <arg>-Xlint</arg>
-            <arg>-Werror</arg>
             <arg>-parameters</arg>
           </compilerArgs>
         </configuration>