name no consumer of this node

A source that documents itself through a specific downstream node depends on
that node to be understood, and that node already depends on this one for
frames. The README pointed at one by name and the CI workflow still carried a
comment about the dataflow that wired it, which no longer exists.

The output is documented by its type instead: wire `image` into anything that
takes std/media/v1/Image. PREVIEW covers seeing the frames without naming
anyone. Generic words like "a viewer" or "a consumer" stay, since they describe
a role rather than a repository.

tests/test_dora_webcam.py

@@ -137,8 +137,8 @@ def test_a_good_read_is_returned_as_is():
     assert frame.shape == (4, 4, 3)
 
 
-def test_the_struct_matches_what_the_viewer_expects():
-    # The viewer respells this schema in its own repository; they share no
+def test_the_struct_matches_the_published_type():
+    # A consumer respells this schema in its own repository; they share no
     # package, so the field names and types are the entire contract.
     assert image.IMAGE_TYPE == pa.struct([
         ("width", pa.uint32()),