Remove unused dependencies

[Celebrate-future]

@ludoch Hi, I am a user of project com.google.appengine:appengine-maven-plugin:1.9.85-SNAPSHOT. I found that its pom file introduced 68 dependencies. However, among them, 13 libraries (19%) have not been used by your project (the redundant dependencies are listed below). This PR helps com.google.appengine:appengine-maven-plugin:1.9.85-SNAPSHOT lose weight :) I have tested the revised configuration in my local environment. It is safe to remove the unused libraries.

Best regards

Redundant dependencies----

javax.transaction:transaction-api:jar:1.1:compile
javax.enterprise:cdi-api:jar:1.0:compile
org.codehaus.plexus:plexus-component-annotations:jar:1.7.1:compile
javax.annotation:jsr250-api:jar:1.0:compile
com.google.code.findbugs:jsr305:jar:3.0.1:compile
javax.validation:validation-api:jar:1.1.0.Final:compile
org.sonatype.plexus:plexus-cipher:jar:1.4:compile
org.sonatype.plexus:plexus-sec-dispatcher:jar:1.4:compile
javax.inject:javax.inject:jar:1:compile
com.google.api-client:google-api-client-servlet:jar:1.21.0:compile
javax.jdo:jdo2-api:jar:2.3-eb:compile
javax.servlet:servlet-api:jar:2.5:compile
io.swagger:swagger-annotations:jar:1.5.9:compile

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[google-cla[bot]]

Thanks for your pull request. It looks like this may be your first contribution to a Google open source project (if not, look below for help). Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA).

:memo: Please visit https://cla.developers.google.com/ to sign.

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