remove docs/html from gitignore #1482

Job	Run time
Tox Checks	21s
Ansible Lint	30s
Check Release Candidate	27s
Discover minimum Python version / Discover minimum Python version	4s
Code Format Check	34s
requirements / Need Requirements Update	34s
Sanity (Ⓐ2.16)	1m 43s
Sanity (Ⓐ2.17)	1m 47s
Sanity (Ⓐ2.18)	1m 31s
Dev EE	0s
Release Version	0s
docs	0s
Release EE	0s
	7m 31s

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