removing colorbar imshow example (#1975)

Author: emmanuelle

doc/python/imshow.md

@@ -5,8 +5,8 @@ jupyter:
     text_representation:
       extension: .md
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-      format_version: '1.1'
-      jupytext_version: 1.1.1
+      format_version: '1.2'
+      jupytext_version: 1.3.0
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     language: python
@@ -97,6 +97,19 @@ fig = px.imshow(img, color_continuous_scale='gray')
 fig.show()
 ```
 
+### Hiding the colorbar when displaying a single-channel image
+
+See [the tutorial on coloraxis](/python/colorscales/#share-color-axis) for more details on coloraxis.
+
+```python
+import plotly.express as px
+from skimage import data
+img = data.camera()
+fig = px.imshow(img, color_continuous_scale='gray')
+fig.update_layout(coloraxis_showscale=False)
+fig.show()
+```
+
 ### Display multichannel image data with go.Image
 
 It is also possible to use the `go.Image` trace from the low-level `graph_objects` API in order to display image data. Note that `go.Image` only accepts multichannel images. For single images, use [`go.Heatmap`](/python/heatmaps).