Changed tomcat-servlet-api to provided scope and removed redundant compile scope def

[acwwat]

identity-toolkit-java-client is used in a web container environment which should already provide the servlet API, so the scope for tomcat-servlet-api can be set to provided instead to avoid being pulled in as an extra packaging dependency.

Also removed the compile scope definitions from dependencies as not specifying a scope already implies a compile scope.

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[acwwat]

I signed it!

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[liujin-google]

Thanks for the contribution Anthony!