Fix 'baseflow' reverse dependency

'airGR' v1.6.11 breaks the CRAN version of the 'baseflow' package. The error was not returned by the automated reverse dependency checking that is running using 'revdepcheck' during the pipeline, but it was detected by the one of the CRAN.

The following error appears only when 'airGR' is not attached before running the example. I don't see where the 'revdepcheck' package does this automatically (by using library() or something else that causes the same behavior).

Package check result: OK

Changes to worse in reverse depends:

Package: baseflow
Check: examples
New result: ERROR
  Running examples in 'baseflow-Ex.R' failed
  The error most likely occurred in:
  
  > base::assign(".ptime", proc.time(), pos = "CheckExEnv")
  > ### Name: BaseflowFilter
  > ### Title: Constructor function of class 'BaseflowFilter'
  > ### Aliases: BaseflowFilter
  > ### Keywords: manip
  > 
  > ### ** Examples
  > 
  > library(baseflow)
  > 
  > # Loading example data from airGR package
  > data(L0123001, package = 'airGR')
  > 
  > # Defining BasinData object
  > 
  > Name <- BasinInfo$BasinName
  > startDate <- BasinObs$DatesR[1]
  > endDate <- BasinObs$DatesR[length(BasinObs$DatesR)]
  > P <- BasinObs$P
  > PET <- BasinObs$E
  > Qobs <- BasinObs$Qmm
  > 
  > BasinData_Example <- BasinData(Name, startDate, endDate, P, PET, Qobs, fill = "GR4J")
  Error in FUN(X[[i]], ...) : object 'RunModel_GR1A' not found
  Calls: BasinData ... CreateInputsModel -> .GetFeatModel -> lapply -> FUN