sql: delete foreign_keys pragma

src/box/sql.c

src/box/sql/CMakeLists.txt

src/box/sql/fkey.c

src/box/sql/insert.c

src/box/sql/pragma.h

src/box/sql/sqliteInt.h

test/sql-tap/tkt-b1d3a2e531.test.lua

test/sql-tap/triggerC.test.lua

test/sql/transitive-transactions.result

test/sql/transitive-transactions.test.lua