Correct jsdoc around goog.ui.Dialog getContent() now that setContent() no longer exists.
Correct jsdoc around goog.ui.Dialog getContent() now that setContent() no longer exists.

RELNOTES: n/a

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=192622572

google/closure-library,teppeis/closure-library,google/closure-library,lucidsoftware/closure-library,google/closure-library,google/closure-library,teppeis/closure-library,lucidsoftware/closure-library,teppeis/closure-library,lucidsoftware/closure-library,lucidsoftware/closure-library,teppeis/closure-library,google/closure-library