Minor documentation correction from code review [ci skip]

Author: eddelbuettel

man/RcppEigen-package.Rd

@@ -17,7 +17,7 @@ Rcpp/Eigen bridge
   package are for illustration only.
 
   As described at the \href{https://libeigen.gitlab.io/}{Eigen project home
-  page} , Eigen is a a C++ template library for linear algebra: matrices,
+  page} , Eigen is a C++ template library for linear algebra: matrices,
   vectors, numerical solvers, and related algorithms.
 }
 \section{Threading}{
@@ -26,7 +26,7 @@ Rcpp/Eigen bridge
   retrieved) explicitly via helper functions \code{EigenSetNbThreads()} and
   \code{EigenNbThreads()}. A default value is stored at package startup; it
   recognises R option value \code{Ncpus} and environment variable
-  \code{OMP_THREAD_LIMITS}.  Additional helper functions
+  \code{OMP_THREAD_LIMIT}.  Additional helper functions
   \code{RcppEigen_throttle_cores()} and \code{RcppEigen_reset_cores()} are
   available to (temporarily) lower the number of cores uses and to reset to
   the package default value set at startup.