Importing change from W3C test repository made by Peter Linss <peter.linss@hp.com> (no bug):  rename multicol-height-001 to multicol-height-002 to avoid file name conflict

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rename : layout/reftests/w3c-css/submitted/multicol3/multicol-height-001.xht => layout/reftests/w3c-css/submitted/multicol3/multicol-height-002.xht
rename : layout/reftests/w3c-css/submitted/multicol3/reference/multicol-height-001.xht => layout/reftests/w3c-css/submitted/multicol3/reference/multicol-height-002.xht