[R-package] remove unnecessary comments (#3356)

* [R-package] remove unused code and comments

* put check back

* other typos

R-package/man/lgb_shared_params.Rd

@@ -4,8 +4,7 @@
 \alias{lgb_shared_params}
 \title{Shared parameter docs}
 \arguments{
-\item{callbacks}{list of callback functions
-List of callback functions that are applied at each iteration.}
+\item{callbacks}{List of callback functions that are applied at each iteration.}
 
 \item{data}{a \code{lgb.Dataset} object, used for training. Some functions, such as \code{\link{lgb.cv}},
 may allow you to pass other types of data like \code{matrix} and then separately supply

R-package/man/lightgbm.Rd

@@ -45,8 +45,7 @@ If early stopping occurs, the model will have 'best_iter' field.}
 
 \item{init_model}{path of model file of \code{lgb.Booster} object, will continue training from this model}
 
-\item{callbacks}{list of callback functions
-List of callback functions that are applied at each iteration.}
+\item{callbacks}{List of callback functions that are applied at each iteration.}
 
 \item{...}{Additional arguments passed to \code{\link{lgb.train}}. For example
 \itemize{

R-package/tests/testthat/test_basic.R

@@ -13,7 +13,7 @@ set.seed(708L)
 #               This is used to mock the situation where an evaluation
 #               metric increases every iteration
 ACCUMULATOR_NAME <- "INCREASING_METRIC_ACUMULATOR"
-assign(x = "INCREASING_METRIC_ACUMULATOR", value = 0.0, envir = .GlobalEnv)
+assign(x = ACCUMULATOR_NAME, value = 0.0, envir = .GlobalEnv)
 
 .increasing_metric <- function(preds, dtrain) {
   if (!exists(ACCUMULATOR_NAME, envir = .GlobalEnv)) {

R-package/tests/testthat/test_metrics.R

 context(".METRICS_HIGHER_BETTER()")
 
-test_that(".METRICS_HIGHER_BETTTER() should be well formed", {
+test_that(".METRICS_HIGHER_BETTER() should be well formed", {
     metrics <- .METRICS_HIGHER_BETTER()
     metric_names <- names(.METRICS_HIGHER_BETTER())
     # should be a logical vector