Fix headings in Create a Sample Type page

[PhilReedData]

https://docs.seek4science.org/help/user-guide/create-sample-type

In the Create Sample type section the top section describes what a Sample Type is - as it should be. But the title of the section does not reflect this. Create a Sample Type is the latter part of the page - that should be a sub-heading

[From Munazah]

[PhilReedData]

https://docs.seek4science.org/help/user-guide/create-sample-type

perhaps first few lines should be one paragraph