sagemathgh-36506: Support launching notebook 7

As reported in sagemath#36414, running `sage -notebook` fails with jupyter
notebook 7.

This seems to be just a matter of a changed import, which we fix.

### 📝 Checklist

- [x] The title is concise, informative, and self-explanatory.
- [x] The description explains in detail what this PR is about.
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Fixes: sagemath#36414

URL: sagemath#36506
Reported by: Gonzalo Tornaría
Reviewer(s): Matthias Köppe

build/pkgs/configure/checksums.ini

@@ -1,4 +1,4 @@
 tarball=configure-VERSION.tar.gz
-sha1=aa7054a0e6a582d2db1475dc47f63a54e6ac569f
-md5=40eab024557ad51e08dfb08e2753a465
-cksum=802824779
+sha1=06f137fde88bc4ee5ce277b1706e258dad6bdce0
+md5=e771b6ed8eaa2f6f706eb0a774685c2e
+cksum=3654829791

build/pkgs/configure/package-version.txt

@@ -1 +1 @@
-c47788b02a42ef4907a0e61e702fbe9bbef27590
+05c386f49cc9961b375274e2e48c05065c5fffe4

src/bin/sage-notebook

@@ -29,7 +29,12 @@ class NotebookJupyter():
     def __init__(self, argv):
         self.print_banner()
         try:
-            from notebook.notebookapp import main
+            try:
+                # notebook 6
+                from notebook.notebookapp import main
+            except ImportError:
+                # notebook 7
+                from notebook.app import main
         except ImportError:
             import traceback
             traceback.print_exc()