Bump swipl to 7.7.4 and stable to 7.6.3.

library/swipl

@@ -1,10 +1,10 @@
 Maintainers: Dave Curylo <[email protected]> (@ninjarobot)
 GitRepo: https://github.com/SWI-Prolog/docker-swipl.git
 
-Tags: latest, 7.7.2
-GitCommit: 7e43714b2b424a54dfef3099c0bc0b27b1e202ef
-Directory: 7.7.2/stretch
+Tags: latest, 7.7.4
+GitCommit: d2a8c332826192ed06732b62a14fd8bfab78a263
+Directory: 7.7.4/stretch
 
-Tags: stable, 7.6.0
-GitCommit: 96f1963cd93da79eecd6fc7442ab301135a982f5
-Directory: 7.6.0/stretch
+Tags: stable, 7.6.3
+GitCommit: d2a8c332826192ed06732b62a14fd8bfab78a263
+Directory: 7.6.3/stretch