Update dependency @grafana/plugin-e2e to v1.12.0 (#1317) #4419

Job	Run time
Run unit tests	1m 0s
Test plugin scaffolding (myorg-nobackend-app, create-plugin --pluginName='no-backend' --orgName='...	1m 55s
Test plugin scaffolding (myorg-backend-app, create-plugin --pluginName='backend' --orgName='myorg...	2m 52s
Test plugin scaffolding (myorg-nobackend-panel, create-plugin --pluginName='no-backend' --orgName...	1m 52s
Test plugin scaffolding (myorg-nobackend-datasource, create-plugin --pluginName='no-backend' --or...	1m 56s
Test plugin scaffolding (myorg-backend-datasource, create-plugin --pluginName='backend' --orgName...	2m 33s
Test plugin scaffolding (myorg-nobackendscenes-app, create-plugin --pluginName='no-backend-scenes...	2m 0s
Release packages	42s
	14m 50s

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