R package dependencies from GitHub should specify commit instead of HEAD in renv.lock

[solarchemist]

It appears (most of) the non-CRAN packages don't actually specify a version (that is, commit) in the renv.lock file.
This could introduce problems if any of the packages change their behaviour in future versions.

# GitHub =============================
- O2solubilitywater   [* -> solarchemist/O2solubilitywater@HEAD]
- common              [* -> solarchemist/R-common@HEAD]
- oceanoptics         [* -> solarchemist/oceanoptics@HEAD]
- photoec             [* -> solarchemist/photoec@cb313098463903e64976befd64c1021775e6ae09]

To do: reinstall these packages using renv::install(...) with a specific commit.