AR6 Global Warming Potential and 2005 county population

GWP values are now consistent with AR6. This affected all sectors - emissions increased slightly across the board. Changes were small enough that the headline text and rounded percentages did not change.
cprg_county_proportions.RDS now includes population back to 2005. Subsequent scripts that use this object consistently filter(year == 2021), so this isn't an issue.
Commit history includes reviewing changes individually across data processing steps.

Minor changes across all sectors (excluding natural systems) by updating GWP values to AR6 [@ipccAR62021].

Additional changes

Some energy data processing to get back to 2005 in _energy/data-raw/MNWI_2005_CensusCrosswalk_UtilityAllocation.R
Text for GWP updated @sec-gwp
Noted differences in LGGIT values @sec-epa-lggit-transportation
Re-ran transportation LGGIT comparison values. Minor change in values
Test values updated for EPA MOVES and GWP
Slight updates to renv package repository locations (RSPM vs. CRAN)
Minor text update in transportation section
Zotero and gitignore updated as needed

Checklist

Please complete this checklist as a courtesy to the PR reviewer.

Code and styling

[x] All of the files/scripts I added are in the right place and named appropriately. See the README for details.
[x] I have not used setwd()
[x] I have used file.path(here::here(), "file_name")) to source any scripts or read in data
[x] I have not added any large datasets, unless absolutely necessary (explain)
[x] I have commented my code, particularly in hard to understand areas
[x] I have added additional package dependencies as necessary with renv::install()
[x] I have run styler::style_dir(".", recursive = TRUE, filetype = c("R", "qmd"))
[x] Plots
- [x] If plotly, use source = "chunk-name" in plot_ly()
- [x] Use formatting with councilR::plotly_layout()?
[x] Chunk formatting
- [x] All chunks named
- [x] All figure or table chunks have caption
- [x] out.width: "95%". If a specific height is needed, use pixels. and/or out.height: "500px"

Document editing

[x] I have ensured that modified documents knit successfully from render_for_publication.R
[x] I have fixed any missing citations, cross references, hyperlinks
[x] I have reviewed my contributions for typos and misspellings.

GitHub and project management

[x] I have identified and assigned at least one Reviewer (Liz, Sam, Laine) to this PR
[x] I have assigned myself to this PR
[x] I have updated the status in the GitHub Project