[R] address some lintr warnings (#8609)

R-package/tests/testthat/test_basic.R

@@ -404,7 +404,7 @@ test_that("Configuration works", {
   config <- xgb.config(bst)
   xgb.config(bst) <- config
   reloaded_config <- xgb.config(bst)
-  expect_equal(config, reloaded_config);
+  expect_equal(config, reloaded_config)
 })
 
 test_that("strict_shape works", {

R-package/tests/testthat/test_dmatrix.R

@@ -53,7 +53,7 @@ test_that("xgb.DMatrix: saving, loading", {
   dtrain <- xgb.DMatrix(tmp_file)
   expect_equal(colnames(dtrain), cnames)
 
-  ft <- rep(c("c", "q"), each=length(cnames)/2)
+  ft <- rep(c("c", "q"), each = length(cnames) / 2)
   setinfo(dtrain, "feature_type", ft)
   expect_equal(ft, getinfo(dtrain, "feature_type"))
 })

R-package/tests/testthat/test_helpers.R

@@ -440,7 +440,7 @@ test_that("xgb.plot.shap.summary works", {
 })
 
 test_that("check.deprecation works", {
-  ttt <- function(a = NNULL, DUMMY=NULL, ...) {
+  ttt <- function(a = NNULL, DUMMY = NULL, ...) {
     check.deprecation(...)
     as.list((environment()))
   }