Remove also `source:maxspeed` when removing `maxspeed` key

[matkoniecz]

reproduced with #12218 PR code (current master version has additional bugs, as I understand)

retagging following tertiary

cycleway:both=separate
highway=tertiary
lanes=2
maxspeed=50
name=Stanisława Mikołajczyka
sidewalk:both=separate
source:maxspeed=PL:urban
surface=asphalt

to "path" results in

name=Stanisława Mikołajczyka
source:maxspeed=PL:urban
highway=path
surface=asphalt

tags

source:maxspeed=PL:urban also should have been removed with maxspeed=50

[matkoniecz]

Additional follow-up for #11696

[tyrasd]

I would do it generally for all source:<tag> prefixed tags when the tag <tag> it removed during a preset change.

Similarly this could be done also for check_date:* tag prefixes. see #12253

[matkoniecz]

yes, definitely - I meant it more generally