Speckles images issues within example notebook

[d33bs]

Discussing with @jenna-tomkinson, the example notebook should be updated for the nuclear speckles dataset to only display filename columns which can display images from the testing dataset.

E.g.

%%time
# view nuclear speckles data with images and overlaid outlines from masks
CytoDataFrame(
    data=f"{nuclear_speckles_path}/test_slide1_converted.parquet",
    data_context_dir=f"{nuclear_speckles_path}/images/plate1",
    data_mask_context_dir=f"{nuclear_speckles_path}/masks/plate1",
)[
    [
        "Metadata_ImageNumber",
        "Nuclei_Number_Object_Number",
        "Image_FileName_A647",
        "Image_FileName_DAPI",
        "Image_FileName_GOLD",
    ]
][:3]

To:

%%time
# view nuclear speckles data with images and overlaid outlines from masks
CytoDataFrame(
    data=f"{nuclear_speckles_path}/test_slide1_converted.parquet",
    data_context_dir=f"{nuclear_speckles_path}/images/plate1",
    data_mask_context_dir=f"{nuclear_speckles_path}/masks/plate1",
)[
    [
        "Metadata_ImageNumber",
        "Nuclei_Number_Object_Number",
        "Image_FileName_DAPI",
    ]
][:3]