Update chart version 1.20.0-rc1 (#2857)

- Update kubernets version 1.23+
- Update post chart install notes with namespace info
- Update upgrade notes in chart

Signed-off-by: Sanket Sudake <sanketsudake@gmail.com>

charts/fission-all/values.yaml

@@ -25,7 +25,7 @@ image: fission/fission-bundle
 ## It is also used by the chart to identify version of the few more images apart from fission-bundle.
 ## Keep it empty for using latest tag.
 ##
-imageTag: v1.19.0
+imageTag: v1.20.0-rc1
 
 ## pullPolicy represents the pull policy to use for images in the chart.
 ##
@@ -99,7 +99,7 @@ fetcher:
   ## image represents the image of the fetcher component.
   image: fission/fetcher
   ## imageTag represents the tag of the image of the fetcher component.
-  imageTag: v1.19.0
+  imageTag: v1.20.0-rc1
 
   ## Fetcher is only for to downloading or uploading archive.
   ## Normally, you don't need to change the value here, unless necessary.
@@ -656,7 +656,7 @@ preUpgradeChecks:
   image: fission/pre-upgrade-checks
   ## pre-install/pre-upgrade checks image version
   ##
-  imageTag: v1.19.0
+  imageTag: v1.20.0-rc1
 
 ## Fission post-install/post-upgrade reporting live in this image
 ##