pgsql: Update plpython_subtransaction alternative expected files

Update plpython_subtransaction alternative expected files

The original patch only targeted Python 2.6 and newer, since that is
what we have supported in PostgreSQL 13 and newer. For older
branches, we need to fix it up for older Python versions.

Branch
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REL_11_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/ba529a6ff41319ea7ad2ab11d2205965e6649a14

Modified Files
--------------
src/pl/plpython/expected/plpython_subtransaction.out | 2 +-
src/pl/plpython/expected/plpython_subtransaction_0.out | 9 ++++++---
src/pl/plpython/expected/plpython_subtransaction_5.out | 9 ++++++---
src/pl/plpython/sql/plpython_subtransaction.sql | 2 +-
4 files changed, 14 insertions(+), 8 deletions(-)