Fix numbering error in CLM50_Tech_Note_Fluxes.rst

[seleneonowe]

Description of changes

Just a tiny two character edit to the surface fluxes documentation.
A link labelled as pointing to an equation for leaf boundary layer resistance was instead pointing to one for canopy air temperature; I've changed it to point to what seems to be the correct equation.

Specific notes

Contributors other than yourself, if any:
N/A

CTSM Issues Fixed (include github issue #):
N/A

Are answers expected to change (and if so in what way)?
N/A

Any User Interface Changes (namelist or namelist defaults changes)?
No.

Does this create a need to change or add documentation? Did you do so?
It is a minor documentation edit.

Testing performed, if any:
(List what testing you did to show your changes worked as expected)
(This can be manual testing or running of the different test suites)
(Documentation on system testing is here: https://github.com/ESCOMP/ctsm/wiki/System-Testing-Guide)
(aux_clm on derecho for intel/gnu and izumi for intel/gnu/nag/nvhpc is the standard for tags on master)

No testing performed.

NOTE: Be sure to check your coding style against the standard
(https://github.com/ESCOMP/ctsm/wiki/CTSM-coding-guidelines) and review
the list of common problems to watch out for
(https://github.com/ESCOMP/CTSM/wiki/List-of-common-problems).

[samsrabin]

Thanks for this, @seleneonowe!

[ekluzek]

This is clearly fixing a legitimate mistype from a quick look at the file. So I'm approving and merging.