examples env: loosen version constraint of nbconvert

examples/Pipfile

@@ -10,7 +10,7 @@ matplotlib = "*"
 seaborn = "*"
 notebook = "*"
 # nbconvert v6.0.2 made `;` suffix on last line ineffective
-nbconvert = "<6.3.1"
+nbconvert = "!=6.0.2"
 
 # python3.7 compatibility
 ipython = "<8"

examples/Pipfile.lock

@@ -1,7 +1,7 @@
 {
     "_meta": {
         "hash": {
-            "sha256": "4a1408555772dff0cf0c853ff0df04e5aa59aa246b2c575b4390bbb02957cdc6"
+            "sha256": "8b083378fbe96029c6de5115d32fc15d29742887e43d524236f4806663ad02c9"
         },
         "pipfile-spec": 6,
         "requires": {