Bump WEEK_12 to v1.6.0, WEEK_4 to 1.7.7 (#2621)

```
WEEK_4: v1.7.7 2024-10-04 37 days ago
WEEK_12: v1.6.0 2024-08-16 87 days ago
```

Author: apivovarov

stablehlo/dialect/Version.cpp

@@ -83,9 +83,9 @@ Version Version::fromCompatibilityRequirement(
     case CompatibilityRequirement::NONE:
       return Version::getCurrentVersion();
     case CompatibilityRequirement::WEEK_4:
-      return Version(1, 7, 5);  // WEEK_4 ANCHOR: DO NOT MODIFY
+      return Version(1, 7, 7);  // WEEK_4 ANCHOR: DO NOT MODIFY
     case CompatibilityRequirement::WEEK_12:
-      return Version(1, 5, 0);  // WEEK_12 ANCHOR: DO NOT MODIFY
+      return Version(1, 6, 0);  // WEEK_12 ANCHOR: DO NOT MODIFY
     case CompatibilityRequirement::MAX:
       return Version::getMinimumVersion();
   }