Update notebooks for JupyterLab 4 upgrade and new SQL cell

[TitoGrine]

The JupyterLab version for notebooks will be updated to version 4.0.4. In JupyterLab 4, the source code of a cell is saved as a single string (likely related to the CodeMirror upgrade). Before, it was an array of strings where each string represented a line of code. Although JupyterLab 4 is still able to read these old notebook files, it seems to append a newline at the end of each string in the array. As a result, every newline in the old notebook gets duplicated. As such, this MR updates the template notebooks to turn the source array of string into a single string.

Additionally, notebooks will now support SQL cells, which are cells specified to run SQL without the need to pre-pend the magic command (i.e. %%sql). To mark a cell as SQL, its metadata needs to contain language: "sql". In the case where a cell used to output the results to a variable, the metadata must also contain output_variable: "<variable>". The notebooks were therefore updated to:

• remove the SQL magic;
• update these cells' metadata accordingly;
• re-word explanation text to mention SQL cell instead of the magic command.

I only updated the SQL cells of notebooks which are currently on the Portal template list.

Note: There will likely also be a further update to the Image Matching with SQL notebook, since boto3 is broken with the new JupyterLab4 upgrade due to an incompatibility with the new version of urllib. A solution for this has not been decided yet.

[TitoGrine]

Closing this PR as it is no longer valid:

• Notebooks should accepts both string and []string options for source, so there is no need to update it here;
• We are not pushing SQL cell just yet, so the templates should continue to refer to %%sql for running SQL.