Make `flower-server` start server with HTTPS by default #4652

Job	Run time
Build, test and upload wheel	1m 12s
Framework / bare	1m 36s
Framework / bare-https	1m 23s
Strategy / FedMedian	1m 5s
Framework / jax	4m 31s
Strategy / FedTrimmedAvg	1m 6s
Framework / pytorch	2m 38s
Strategy / QFedAvg	1m 11s
Framework / tensorflow	3m 12s
Strategy / FaultTolerantFedAvg	1m 9s
Framework / tabnet	2m 33s
Framework / opacus	2m 34s
Strategy / FedAvgM	1m 6s
Framework / pytorch-lightning	2m 23s
Strategy / FedAdam	1m 5s
Framework / mxnet	1m 37s
Strategy / FedAdagrad	1m 11s
Framework / scikit-learn	2m 10s
Strategy / FedYogi	1m 9s
Framework / fastai	3m 41s
Framework / pandas	1m 27s
	39m 59s

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