[minor] remove dead code in ExpressionEvalHelper

[cloud-fan]

What changes were proposed in this pull request?

This addresses https://github.com/apache/spark/pull/21236/files#r207078480

both #21236 and #21838 add a InternalRow result check to ExpressionEvalHelper and becomes duplicated.

How was this patch tested?

N/A

[holdensmagicalunicorn]

@cloud-fan, thanks! I am a bot who has found some folks who might be able to help with the review:@ueshin, @rxin and @JoshRosen

[cloud-fan]

cc @srowen@gatorsmile

[gatorsmile]

LGTM

[SparkQA]

Test build #93949 has finished for PR 21958 at commit 19dd614.

• This patch fails due to an unknown error code, -9.
• This patch merges cleanly.
• This patch adds no public classes.

[ueshin]

Jenkins, retest this please.

[ueshin]

LGTM.

[SparkQA]

Test build #93976 has finished for PR 21958 at commit 19dd614.

• This patch fails Spark unit tests.
• This patch merges cleanly.
• This patch adds no public classes.

[cloud-fan]

retest this please

[SparkQA]

Test build #93987 has finished for PR 21958 at commit 19dd614.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds no public classes.

[srowen]

Thanks, merged to master