DOC: Remove dead .cid references to lost visual PNGs

PR #440 added 20 .cid
references for example-visual PNGs in Core/Common/. The CIDs were
computed locally by the contributor but the underlying binaries were
never published to ITKTestingData and IPFS pinning has expired, so
every fetch attempt (gh-pages CID/, data.kitware.com, itk.org,
ipfs.io, dweb.link, w3s.link, nftstorage, pinata, filebase) now
returns 404 / error pages.

Building with Module_SphinxExamples=ON consequently fails 20
ExternalData fetches per configure. Remove the dead .cid files and
the matching .. figure:: blocks (with their :scale:/:alt:/caption
lines) from the affected Documentation.rst so the module builds
cleanly. Real output PNGs (e.g. MakePartOfImageTransparent.png) and
all unrelated content are untouched.

Affected examples (Core/Common):
  ApplyAFilterOnlyToASpecifiedRegionOfAnImage, ApplyCustomOperationToEachPixelInImage,
  BoundingBoxOfAPointSet, BresenhamLine, ConvertArrayToImage,
  CreateDerivativeKernel, CreateGaussianKernel, CreateVectorImage,
  CropImageBySpecifyingRegion, ImageRegionIntersection,
  MakePartOfImageTransparent, MiniPipeline, ReadAPointSet.

If the original visuals are recovered, the figure references can be
restored together with the binaries in a follow-up.

Assisted-by: Claude Code (claude-opus-4-7) -- audit of missing data sources and .rst cleanup.

Author: hjmjohnson

src/Core/Common/ApplyAFilterOnlyToASpecifiedRegionOfAnImage/Documentation.rst

@@ -25,11 +25,6 @@ That is, to tell the DerivativeImageFilter to only operate on a small region, yo
 Results
 -------
 
-.. figure:: Relationship.png
-  :scale: 70%
-  :alt: relationship.png
-
-
 Code
 ----
 

src/Core/Common/ApplyAFilterOnlyToASpecifiedRegionOfAnImage/Relationship.png.cid

@@ -10,11 +10,6 @@ Synopsis
 --------
 Apply a custom operation to each pixel in an image.
 
-.. figure:: Relationship.png
-  :scale: 70%
-  :alt: Relationship.png
-
-
 .. figure:: Operator.png
   :scale: 70%
   :alt: Operator.png

src/Core/Common/ApplyCustomOperationToEachPixelInImage/Documentation.rst

@@ -16,10 +16,6 @@ Get the bounding box of a PointSet
 
 Results
 -------
-.. figure:: BoundingBox.png
-  :scale: 70%
-  :alt: BoundingBox.png
-
 Output::
   bounds: [0, 0.1, 0, 0.1, 0, 0]
   center: [0.05, 0.05, 0]

src/Core/Common/ApplyCustomOperationToEachPixelInImage/Operation.png.cid

@@ -14,16 +14,6 @@ Get the points on a Bresenham line between two points.
 
 Results
 -------
-.. figure:: Segmentation.png
-  :scale: 70%
-  :alt: Segmentation.png
-
-  ITK's Bresenham's Line algorithm is used and optimized for voxel traversal operations.
-
-.. figure:: Operation.png
-  :scale: 70%
-  :alt: Operation.png
-
 Output::
 
   [0, 0]