[Regression] Incorrect filename in test case comment

While browsing the test cases, found that the incorrect filename was there in the test case comment.
The below commit added the custom hash opclass in insert.sql,

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commit fafec4cce814b9b15991b62520dc5e5e84655a8a
Author: Alvaro Herrera <alvherre@alvh.no-ip.org>
Date:   Fri Apr 13 12:27:22 2018 -0300

    Use custom hash opclass for hash partition pruning
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and later below commit moved those to test_setup.sql

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    Rearrange core regression tests to reduce cross-script dependencies. 
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but we haven't changed the filename in other test cases.
Did the same in the attached patch.

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