Update deploy to Heroku instructions

[samharrison7]

As per issue #1047, Voila v0.3 requires --Voila.ip=0.0.0.0 to be explicitly set when deploying to Heroku. I have updated the deploy.rst docs to reflect this.

I also updated the Python runtime to the latest version that is supported by all Heroku stacks.

References

#1047

Code changes

Only changes to docs as described above.

User-facing changes

No user facing changes (except to documentation).

Backwards-incompatible changes

No backwards incompatible changes.

[github-actions]

👈 Launch a Binder on branch samharrison7/voila/patch-1

[github-actions]

Benchmark report

The execution time (in milliseconds) are grouped by test file, test type and browser.
For each case, the following values are computed: min <- [1st quartile - median - 3rd quartile] -> max.

Results table

Test file	voila-tree-classic.ipynb	voila-tree-light.ipynb	voila-tree-dark.ipynb	voila-tree-miami.ipynb	basics.ipynb	bqplot.ipynb	dashboard.ipynb	gridspecLayout.ipynb	interactive.ipynb	ipympl.ipynb	ipyvolume.ipynb	multiple_widgets.ipynb	query-strings.ipynb	reveal.ipynb
Render
chromium
actual	106 <- [114 - 131 - 164] -> 257	84 <- [89 - 96 - 113] -> 153	81 <- [86 - 96 - 110] -> 142	79 <- [82 - 90 - 105] -> 128	2924 <- [3096 - 3169 - 3244] -> 4113	2990 <- [3018 - 3039 - 3119] -> 3610	3424 <- [3517 - 3571 - 3832] -> 4374	3319 <- [3386 - 3545 - 3705] -> 3932	2358 <- [2378 - 2432 - 2541] -> 2918	4582 <- [4703 - 4919 - 5277] -> 6396	9858 <- [12407 - 12679 - 13085] -> 13500	8825 <- [8828 - 8850 - 8908] -> 9133	1775 <- [1779 - 1822 - 1823] -> 1861	3183 <- [3337 - 3622 - 3993] -> 5180
expected	3379 <- [3442 - 3517 - 3701] -> 3876	2976 <- [3227 - 3321 - 3421] -> 3604	3608 <- [3623 - 3709 - 3793] -> 3825	4453 <- [4453 - 4523 - 4661] -> 4748	2559 <- [2655 - 2656 - 2660] -> 2674	3982 <- [4079 - 4213 - 4356] -> 4743	12183 <- [18509 - 19553 - 20811] -> 21515	15319 <- [15660 - 15796 - 15912] -> 16056	1517 <- [1920 - 1997 - 2103] -> 2113

❗ Test metadata have changed

--- /dev/fd/63	2022-05-31 17:00:00.753154587 +0000
+++ /dev/fd/62	2022-05-31 17:00:00.753154587 +0000
@@ -4,7 +4,7 @@
     "BENCHMARK_REFERENCE": "actual"
   },
   "browsers": {
-    "chromium": "97.0.4666.0"
+    "chromium": "94.0.4595.0"
   },
   "systemInformation": {
     "cpu": {
@@ -34,7 +34,7 @@
       "voltage": ""
     },
     "mem": {
-      "total": 7283838976
+      "total": 7291699200
     },
     "osInfo": {
       "arch": "x64",
@@ -42,11 +42,11 @@
       "codename": "Focal Fossa",
       "codepage": "UTF-8",
       "distro": "Ubuntu",
-      "kernel": "5.13.0-1023-azure",
+      "kernel": "5.8.0-1040-azure",
       "logofile": "ubuntu",
       "platform": "linux",
-      "release": "20.04.4 LTS",
-      "serial": "b0ef5d8b9e374e1e89c1a98defc7c0cc",
+      "release": "20.04.3 LTS",
+      "serial": "cfc067bfcb844f35865e279a1b0e66c5",
       "servicepack": "",
       "uefi": false
     }

[trungleduc]

Thanks!