Fixing built jar location in readme

[nirajpatel]

JAR location in readme is incorrect.

[tensorflow-jenkins]

Can one of the admins verify this patch?

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[nirajpatel]

I signed it!

[googlebot]

CLAs look good, thanks!

[teamdandelion]

@jart ptal

[teamdandelion]

@tensorflow-jenkins test this please
then i will merge it either way since it just a readme change....