Rename 'variable' column to work around plotly bug

[bpbond]

See https://github.com/COMPASS-DOE/TEMPEST/issues/97#issuecomment-1572588633

Weird. No error being thrown on one machine, but on my and @stephpenn1 's laptops, line 242 in server.R was generating:

plotly::ggplotly(b)
Error in tidyr::pivot_longer(data = layout$layout, cols = paste0(x, c("_min",  : 
  Names must be unique.
✖ These names are duplicated:
  * "variable" at locations 4 and 13.
ℹ Use argument `names_repair` to specify repair strategy.

Anyway, as a workaround this PR simply renames the 'variable' column in the TEROS data frame. Things now seem to work fine but please test

[stephpenn1]

looks great thanks