Update install-and-use-asciidoctor-java-integration.adoc

Corrected two examples that show the use of Collections.<String,Object>emptyMap() to create an empty map as the options parameter. Doing this results in a Java UnsupportedOperationException at runtime because AsciiDoctor is trying to put something in the immutable map that's returned (see stack trace below).

java.lang.UnsupportedOperationException
	at java.util.AbstractMap.put(AbstractMap.java:203)
	at org.asciidoctor.internal.JRubyAsciidoctor.addRubyRuntimeAsAttribute(JRubyAsciidoctor.java:174)
	at org.asciidoctor.internal.JRubyAsciidoctor.renderFile(JRubyAsciidoctor.java:158)