[ci] fixed r-lintr version constraint (#2990)

* Update test.sh

* update brew to pull new URL for basictex

.ci/test.sh

@@ -48,7 +48,7 @@ if [[ $TRAVIS == "true" ]] && [[ $TASK == "lint" ]]; then
     conda install -q -y -n $CONDA_ENV \
         -c conda-forge \
             libxml2 \
-            r-lintr>=2.0
+            "r-lintr>=2.0"
     pip install --user cpplint
     echo "Linting Python code"
     pycodestyle --ignore=E501,W503 --exclude=./compute,./.nuget . || exit -1

.ci/test_r_package.sh

@@ -35,6 +35,10 @@ fi
 # Installing R precompiled for Mac OS 10.11 or higher
 if [[ $OS_NAME == "macos" ]]; then
 
+    # temp fix for basictex
+    if [[ $AZURE == "true" ]]; then
+        brew update
+    fi
     brew install qpdf
     brew cask install basictex
     export PATH="/Library/TeX/texbin:$PATH"