Fix default docker_observer endpoint on Windows #85278

Job	Run time
windows-unittest-matrix (receiver-0)	19m 10s
windows-unittest-matrix (receiver-1)	19m 20s
windows-unittest-matrix (receiver-2)	17m 33s
windows-unittest-matrix (receiver-3)	14m 43s
windows-unittest-matrix (processor-0)	7m 15s
windows-unittest-matrix (processor-1)	10m 24s
windows-unittest-matrix (exporter-0)	9m 43s
windows-unittest-matrix (exporter-1)	18m 8s
windows-unittest-matrix (exporter-2)	14m 33s
windows-unittest-matrix (exporter-3)	14m 31s
windows-unittest-matrix (extension)	11m 54s
windows-unittest-matrix (connector)	11m 1s
windows-unittest-matrix (internal)	13m 28s
windows-unittest-matrix (pkg)	10m 10s
windows-unittest-matrix (cmd-0)	2m 41s
windows-unittest-matrix (cmd-1)	12m 30s
windows-unittest-matrix (other)	12m 42s
windows-unittest	0s
	3h 39m 46s

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