Make 'neon.protocol_version = 2' the default, take two (#7819)

Once all the computes in production have restarted, we can remove
protocol version 1 altogether.

See issue #6211.

This was done earlier already in commit 0115fe6, but reverted before
it was released to production in commit bbe730d because of issue
#7692. That issue was fixed
in commit 22afaea, so we are ready to change the default again.

pgxn/neon/libpagestore.c

@@ -49,7 +49,7 @@ char	   *neon_auth_token;
 int			readahead_buffer_size = 128;
 int			flush_every_n_requests = 8;
 
-int         neon_protocol_version = 1;
+int         neon_protocol_version = 2;
 
 static int	n_reconnect_attempts = 0;
 static int	max_reconnect_attempts = 60;
@@ -860,7 +860,7 @@ pg_init_libpagestore(void)
 							"Version of compute<->page server protocol",
 							NULL,
 							&neon_protocol_version,
-							1, /* default to old protocol for now */
+							2, /* use protocol version 2 */
 							1, /* min */
 							2, /* max */
 							PGC_SU_BACKEND,