doc: remove gitter and and discord and github discussions #3014

Job	Run time
lint_test_generate	2m 27s
has_mapbox_token	1s
publish	0s
CI requiring tokens / Android/Mapbox/Fabric / Android Example Build Fabric mapbox	13m 46s
CI requiring tokens / Android/Mapbox11 / Android Example Build Paper mapbox11	8m 11s
CI requiring tokens / iOS/Mapbox / iOS Example Build Paper mapbox	29m 13s
CI requiring tokens / Android/Mapbox / Android Example Build Paper mapbox	8m 9s
CI requiring tokens / iOS/Mapbox11 / iOS Example Build Paper mapbox11	34m 35s
CI requiring tokens / iOS/Mapbox/Fabric / iOS Example Build Fabric mapbox	17m 16s
CI requiring tokens / Web/Mapbox / Example Build for Web	1m 23s
	1h 55m 1s

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