add |+| based on AMT mif

[orichters]

Purpose of this PR

• to have consistent use of |+| notation across REMIND mif and piamInterfaces

library(tidyverse)
devtools::load_all()
vars <- levels(quitte::as.quitte("/p/projects/remind/modeltests/remind/output/SSP2-NPi-AMT_2025-02-21_22.17.03/REMIND_generic_SSP2-NPi-AMT.mif")$variable)
for (m in names(mappingNames())) {
  d <- getMapping(m)
  for (v in vars) {
    d$piam_variable[deletePlus(d$piam_variable) == deletePlus(v)] <- v
  }
  writeMapping(d, paste0("inst/mappings/mapping_", m, ".csv"))
}