Clarify the order in which sources are applied in docs of `_.assign`, `_.defaults`, and `_.merge`. [ci skip]
Clarify the order in which sources are applied in docs of `_.assign`, `_.defaults`, and `_.merge`. [ci skip]

jshanson7/lodash,enng0227/lodash,Droogans/lodash,rlugojr/lodash,Droogans/lodash,beaugunderson/lodash,mshoaibraja/lodash,tonyonodi/lodash,huyinghuan/lodash,msmorgan/lodash,benweet/lodash,tquetano-r7/lodash,woldie/lodash,Xotic750/lodash,msmorgan/lodash,tonyonodi/lodash,zestia/lodash,mshoaibraja/lodash,zestia/lodash,prawnsalad/lodash,benweet/lodash,Droogans/lodash,mshoaibraja/lodash,huyinghuan/lodash,prawnsalad/lodash,beaugunderson/lodash,rlugojr/lodash,steelsojka/lodash,jshanson7/lodash,boneskull/lodash,huyinghuan/lodash,jshanson7/lodash,enng0227/lodash,Xotic750/lodash,Xotic750/lodash,woldie/lodash,boneskull/lodash,tquetano-r7/lodash,steelsojka/lodash,tquetano-r7/lodash,enng0227/lodash,zestia/lodash,prawnsalad/lodash,benweet/lodash,woldie/lodash