Generators/HTML: only display a TOC when there is more than one doc #2072

Job	Run time
Build Phar on PHP: 8.0	28s
Coverage: 8.4 (Linux)	4m 16s
Coverage: 8.4 (Win)	1m 42s
Coverage: 5.4 (Linux)	25m 40s
Coverage: 5.5 (Win)	2m 21s
Coverage: 7.2 with custom ini settings (Linux)	5m 36s
PHP: 5.4 (Linux)	1m 6s
PHP: 5.5 (Linux)	7m 39s
PHP: 5.6 (Linux)	5m 49s
PHP: 7.0 (Linux)	1m 30s
PHP: 7.1 (Linux)	1m 21s
PHP: 7.2 (Linux)	1m 22s
PHP: 7.3 (Linux)	52s
PHP: 7.4 (Linux)	48s
PHP: 8.0 (Linux)	50s
PHP: 8.1 (Linux)	48s
PHP: 8.2 (Linux)	53s
PHP: 8.3 (Linux)	49s
PHP: 8.4 (Linux)	28s
PHP: 8.5 (Linux)	51s
PHP: 5.5 (Win)	1m 18s
PHP: 5.6 (Win)	5m 39s
PHP: 7.0 (Win)	1m 36s
PHP: 7.1 (Win)	1m 27s
PHP: 7.2 (Win)	1m 19s
PHP: 7.3 (Win)	1m 0s
PHP: 7.4 (Win)	48s
PHP: 8.0 (Win)	50s
PHP: 8.1 (Win)	51s
PHP: 8.2 (Win)	50s
PHP: 8.3 (Win)	49s
PHP: 8.4 (Win)	30s
PHP: 8.5 (Win)	59s
PHP: 5.5 with custom ini settings (Linux)	6m 42s
PHP: 7.0 with custom ini settings (Linux)	1m 7s
coveralls-finish	5s
	1h 30m 59s

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