doc: Clarify dem_mosaic doc
doc: Clarify dem_mosaic doc

NeoGeographyToolkit/StereoPipeline,NeoGeographyToolkit/StereoPipeline,oleg-alexandrov/StereoPipeline,NeoGeographyToolkit/StereoPipeline,njwilson23/StereoPipeline,oleg-alexandrov/StereoPipeline,DougFirErickson/StereoPipeline,oleg-alexandrov/StereoPipeline,njwilson23/StereoPipeline,NeoGeographyToolkit/StereoPipeline,DougFirErickson/StereoPipeline,DougFirErickson/StereoPipeline,DougFirErickson/StereoPipeline,ScottMcMichael/StereoPipeline,DougFirErickson/StereoPipeline,ScottMcMichael/StereoPipeline,njwilson23/StereoPipeline,ScottMcMichael/StereoPipeline,njwilson23/StereoPipeline,oleg-alexandrov/StereoPipeline,NeoGeographyToolkit/StereoPipeline,oleg-alexandrov/StereoPipeline,njwilson23/StereoPipeline,ScottMcMichael/StereoPipeline,oleg-alexandrov/StereoPipeline,DougFirErickson/StereoPipeline,ScottMcMichael/StereoPipeline,NeoGeographyToolkit/StereoPipeline,ScottMcMichael/StereoPipeline,njwilson23/StereoPipeline