[GR-53454] Warn when @ReportPolymorphism is used incorrectly

[graalvmbot]

• Remove duplicate .required() check.

It looks like this:

truffleruby/src/main/java/org/truffleruby/cext/CExtNodes.java:1054: warning: This node uses @ReportPolymorphism but has a single specialization, so the annotation has no effect.
    public abstract static class RbGvGetNode extends PrimitiveArrayArgumentsNode {
                           ^
truffleruby/src/main/java/org/truffleruby/core/array/ArrayNodes.java:1803: warning: This node uses @ReportPolymorphism but has a single specialization, so the annotation has no effect.
    public abstract static class ReplaceNode extends CoreMethodNode {
                           ^