dea_tool.plotting.rgb adding custom titles causes error due to attribute error "missing axs object"

[jennaguffogg]

Describe the bug/issue
When trying to give a plot a custom title, an attribute error occurs due to missing 'axs' attribute.
ie:

AttributeError: 'AxesImage' object has no attribute 'axs'

Steps to reproduce
Steps to reproduce the behaviour. For example:

1. Open DEA Sandbox
2. Launch the "DEA_products/DEA_GeoMAD.ipynb" notebook
3. in code cell 6, attempt to add 'titles' to the plotting function:
   rgb(ds, bands=["nbart_red", "nbart_green", "nbart_blue"], titles=pd.Timestamp(ds.time.values[0]).year)

Expected behaviour
The title in the output image should have been the year of the geomedian product ie '2021'