Add `Href.clear_href` #816

Job	Run time
test-ubuntu-with-pgstac	32s
test-ubuntu-with-gdal	3m 12s
test-ubuntu (-p stac)	41s
test-windows	4m 5s
test-ubuntu (-p stac -F reqwest)	1m 47s
check	1m 35s
check-nightly	1m 17s
test-ubuntu (-p stac-api)	17s
test-ubuntu (-p stac -p stac-api -F geo)	1m 6s
clippy	54s
test-ubuntu (-p stac-arrow)	1m 21s
doc	1m 52s
fmt	23s
test-ubuntu (-p stac-async)	2m 31s
test-macos	1m 14s
test-ubuntu (-p stac-cli --no-default-features)	50s
validate-stac-server	1m 47s
test-ubuntu (-p stac-geoparquet)	1m 42s
validate-stac-server-pgstac	1m 19s
test-ubuntu (-p stac-server --no-default-features)	45s
test-ubuntu (-p stac-server --no-default-features -F axum)	51s
test-ubuntu (-p stac-server --no-default-features -F memory-item-search)	47s
test-ubuntu (-p stac-server)	52s
test-ubuntu (-p stac-validate)	1m 0s
	32m 40s

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