Fix dependency declarations: dplyr should be in Imports; abind and reshape2 are unused

[joethorley]

While reviewing the package, three dependency-declaration issues surfaced:

1. dplyr is in Suggests but used unconditionally in package code. dplyr:: is called in 13 files in R/ (e.g. R/hc.R, R/hcp-ma.R, R/gof.R, R/tidy.R, R/glance.R, R/plot-cdf.R, ...). A package whose exported functions call dplyr:: must declare it in Imports; otherwise R CMD check flags it and the functions fail at runtime when dplyr is not installed. → move dplyr to Imports.

2. abind is in Imports but never used. The only reference is #' @importFrom abind abind in R/ssdtools-package.R; abind() is never called. → remove abind from Imports and drop the @importFrom.

3. reshape2 is in Suggests but never used anywhere in R/, tests/, or vignettes/. reshape2 is also a superseded/discouraged package. → remove from Suggests.

Note: plyr is retained — it is genuinely used (plyr::summarise() in R/ggproto.R). Replacing it has different semantics and is out of scope here.

These are low-risk declaration changes with no change to package behaviour. A PR follows.

[joethorley]

Update: the fix is being routed through the poissonconsulting/ssdtools fork (which is ahead of bcgov/main):

• dplyr → Imports and reshape2 removal are already on poissonconsulting/main.
• Unused abind removal: Remove unused abind dependency poissonconsulting/ssdtools#171.

These will land on bcgov/main via the fork's normal upstream flow. PR #477 (against bcgov/main directly) was closed in favour of the fork PR. plyr was also removed on the fork (it refactored away the single plyr::summarise() use).