pgsql: Fix some comments in xlogreader.h

Fix some comments in xlogreader.h

segment_open and segment_close were mentioned with incorrect names.

Discussion: /messages/by-id/20200525234944.GA1573@paquier.xyz

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/f93bb0ce64005c84e1d1d431eed31e0da4835078

Modified Files
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src/include/access/xlogreader.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)