Update sphinx_rtd_theme to 68a19ca / 0.4.3.dev0.

[Chris Johns]

On 26/2/20 3:28 pm, Amar Takhar wrote:
> On 2020-02-26 15:27 +1100, Chris Johns wrote:
>>
>> Great, I am OK with the patch being pused. If it breaks on sync it will show in
>> the build not updating and I am sure we can sort it out.
> 
> Okay great I'll do that now then thank you!
> 

The online docs failed to build. The error is:

Theme error:
unsupported theme option 'genindex' given

Has the minimum required version of Sphinx changed from 1.3 to something else?

Chris