Property 'http://javax.xml.XMLConstants/property/accessExternalDTD

[dixonwhitmire]

This PR resolves an issue where an Apache Tika transitive dependency, xerces, generates the following stack trace and warning

org.xml.sax.SAXNotRecognizedException: Property 'http://javax.xml.XMLConstants/property/accessExternalDTD' is not recognized.
        at org.apache.xerces.jaxp.validation.XMLSchemaFactory.setProperty(Unknown Source)
        at org.apache.camel.support.processor.validation.SchemaReader.createSchemaFactory(SchemaReader.java:184)
        at org.apache.camel.support.processor.validation.SchemaReader.getSchemaFactory(SchemaReader.java:157)
        at org.apache.camel.support.processor.validation.SchemaReader.createSchema(SchemaReader.java:198)
        at org.apache.camel.support.processor.validation.SchemaReader.loadSchema(SchemaReader.java:89)
        at org.apache.camel.component.validator.ValidatorEndpoint.createProducer(ValidatorEndpoint.java:121)

https://bugs.openjdk.java.net/browse/JDK-8200177
https://stackoverflow.com/questions/58374278/org-xml-sax-saxnotrecognizedexception-property-http-javax-xml-xmlconstants-p

Removing the xerces implementation allows the application to utilize the appropriate implementations that are now included with the JRE/JDK.

I also updated LFH connect's camel dependency from 3.4 to 3.7.1.

Note: I was able to determine which library "pulled' in xerces using the ./gradlew dependencies command.

resolves #418