v1.4.0-rc.1

Fixes included in this RC:

• Update pipelines to 1.7.0 #1997
• Update KFP Tekton for version 1.0.0 #2006
• Use MPI operator tag v0.3.0 #2019
• Update manifests for Katib 0.12.0-rc.1 release #2008
• Update Notebooks WG manifests from RC1 #2021
• feat: add seldon permissions to default-editor #2013
• git: Ignore Vim files #2020
• Add 1.4 release information #1974
• docs: fix fmt #1992
• handbook: Allocate 3 weeks for distribution testing #1996
• Update README for pipelines 1.7.0 #1999

Fixes included from the previous RC0

• #2018
• #2005
• #1985