RFR: 8279528: Unused TypeEnter.diag after JDK-8205187

[Vicente Romero]

On Wed, 5 Jan 2022 16:58:33 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

> SonarCloud reports that `TypeEnter.diag` is not used. The last use was removed by [JDK-8205187](https://bugs.openjdk.java.net/browse/JDK-8205187). We can probably save a few bytes/cycles by not retaining it.

looks good

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Marked as reviewed by vromero (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/6971