sqlite3.go: Remove -DSQLITE_ENABLE_FTS4_UNICODE61: not supported (#872)

This option was enabled by default in sqlite3 on 2014-07-03.
This setting does nothing. It can now be disabled with
SQLITE_DISABLE_FTS3_UNICODE. See the upstream commit:
https://sqlite.org/src/info/0cc0230ae9cfc976

I think this change was imported into this project with commit
ee9da48 on 2015-06-12.

sqlite3.go

@@ -15,7 +15,6 @@ package sqlite3
 #cgo CFLAGS: -DHAVE_USLEEP=1
 #cgo CFLAGS: -DSQLITE_ENABLE_FTS3
 #cgo CFLAGS: -DSQLITE_ENABLE_FTS3_PARENTHESIS
-#cgo CFLAGS: -DSQLITE_ENABLE_FTS4_UNICODE61
 #cgo CFLAGS: -DSQLITE_TRACE_SIZE_LIMIT=15
 #cgo CFLAGS: -DSQLITE_OMIT_DEPRECATED
 #cgo CFLAGS: -DSQLITE_DEFAULT_WAL_SYNCHRONOUS=1