pgsql: config: Rename "Asynchronous Behavior" to "I/O"

config: Rename "Asynchronous Behavior" to "I/O"

"I/O" seems more descriptive than "Asynchronous Behavior", given that some of
the GUCs in the section don't relate to anything asynchronous.

Most other abbreviations in the config sections are un-abbreviated, but
"Input/Output" seems less likely to be helpful than just IO or I/O.

Reviewed-by: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Discussion: https://postgr.es/m/x3tlw2jk5gm3r3mv47hwrshffyw7halpczkfbk3peksxds7bvc@lguk43z3bsyq

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/4dd09a1d415d143386d5e6dc9519615a8b18f850

Modified Files
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doc/src/sgml/config.sgml | 4 ++--
src/backend/utils/misc/guc_tables.c | 10 +++++-----
src/backend/utils/misc/postgresql.conf.sample | 2 +-
src/include/utils/guc_tables.h | 2 +-
4 files changed, 9 insertions(+), 9 deletions(-)