pgsql: plpython: Fix sed expression in python3 build

plpython: Fix sed expression in python3 build

The old expression sed 's,$(srcdir),python3,' would normally resolve
as sed 's,.,python3,', which is not really what we wanted. While it
doesn't actually break anything right now, it's still wrong, so put in
a bit more work to make it more robust.

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/04e5cb629b5c46462eee334f68d5ea12bc9097e0

Modified Files
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src/pl/plpython/Makefile | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)