pgsql: doc: remove xreflabels from commits 75fcdd2ae2 and 85af628da5

doc:  remove xreflabels from commits 75fcdd2ae2 and 85af628da5

xreflabels prevent references to the chapter numbers of sections id's.
It should only be used in specific cases.

Discussion: https://postgr.es/m/8315c0ca-7758-8823-fcb6-f37f9413e6b6@2ndquadrant.com

Backpatch-through: 9.5

Branch
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REL9_6_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/f6ee4c39aca943aa224b410895f3634e0f1f60bc

Modified Files
--------------
doc/src/sgml/ecpg.sgml        | 2 +-
doc/src/sgml/geqo.sgml        | 2 +-
doc/src/sgml/gin.sgml         | 2 +-
doc/src/sgml/gist.sgml        | 2 +-
doc/src/sgml/libpq.sgml       | 2 +-
doc/src/sgml/maintenance.sgml | 2 +-
doc/src/sgml/plperl.sgml      | 2 +-
doc/src/sgml/plpgsql.sgml     | 2 +-
doc/src/sgml/plpython.sgml    | 2 +-
doc/src/sgml/spgist.sgml      | 2 +-
doc/src/sgml/spi.sgml         | 2 +-
doc/src/sgml/storage.sgml     | 2 +-
doc/src/sgml/vacuumlo.sgml    | 2 +-
13 files changed, 13 insertions(+), 13 deletions(-)