Adjust to ObjFW changes

FossilOrigin-Name: b80a03bd2fd4ff11dc0d9c7ce330695ebc060f78034b9ade2d7eb53d88c7bb80

src/exceptions/PGException.m

@@ -1,6 +1,8 @@
 #import "PGException.h"
 
 @implementation PGException
+@synthesize connection = _connection;
+
 + (instancetype)exceptionWithConnection: (PGConnection*)connection
 {
 	return [[[self alloc] initWithConnection: connection] autorelease];
@@ -36,9 +38,4 @@
 	return [OFString stringWithFormat: @"A PostgreSQL operation failed: %@",
 					   _error];
 }
-
-- (PGConnection*)connection
-{
-	OF_GETTER(_connection, NO)
-}
 @end