Revert "use version of graal that has whitelisted BigInteger.signum"

This reverts commit 1b54125047f440800597553cce714716db359b36.

Author: timfel

mx.graalpython/suite.py

@@ -44,23 +44,23 @@
             },
             {
                 "name": "tools",
-                "version": "c7273c45300de62de498453fbad5e8bf637e5c4e",
+                "version": "b47aaf48144cbc9445cea8fdc37735e3924339fa",
                 "subdir": True,
                 "urls": [
                     {"url": "https://github.com/oracle/graal", "kind": "git"},
                 ],
             },
             {
                 "name": "sulong",
-                "version": "c7273c45300de62de498453fbad5e8bf637e5c4e",
+                "version": "b47aaf48144cbc9445cea8fdc37735e3924339fa",
                 "subdir": True,
                 "urls": [
                     {"url": "https://github.com/oracle/graal", "kind": "git"},
                 ]
             },
             {
                 "name": "regex",
-                "version": "c7273c45300de62de498453fbad5e8bf637e5c4e",
+                "version": "b47aaf48144cbc9445cea8fdc37735e3924339fa",
                 "subdir": True,
                 "urls": [
                     {"url": "https://github.com/oracle/graal", "kind": "git"},