[ci] nose is not needed anymore (#2151)

.appveyor.yml

-version: 2.2.4.{build}
+version: 2.2.4.{build}
 
 image: Visual Studio 2015
 platform: x64
@@ -29,7 +29,7 @@ install:
   - ps: $env:LGB_VER = (Get-Content VERSION.txt).trim()
   - conda config --set always_yes yes --set changeps1 no
   - conda update -q -y conda
-  - conda create -q -y -n test-env python=%PYTHON_VERSION% matplotlib nose numpy pandas psutil pytest python-graphviz scikit-learn scipy
+  - conda create -q -y -n test-env python=%PYTHON_VERSION% matplotlib numpy pandas psutil pytest python-graphviz scikit-learn scipy
   - activate test-env
   - set PATH=%CONDA_PREFIX%\Library\bin\graphviz;%PATH%  # temp graphviz hotfix
 

.ci/test.sh

@@ -79,7 +79,7 @@ if [[ $TASK == "if-else" ]]; then
     exit 0
 fi
 
-conda install -q -y -n $CONDA_ENV matplotlib nose numpy pandas psutil pytest python-graphviz scikit-learn scipy
+conda install -q -y -n $CONDA_ENV matplotlib numpy pandas psutil pytest python-graphviz scikit-learn scipy
 
 if [[ $OS_NAME == "macos" ]] && [[ $COMPILER == "clang" ]]; then
     sudo ln -sf `ls -d "$(brew --cellar libomp)"/*/lib`/* $CONDA_PREFIX/lib || exit -1  # fix "OMP: Error #15: Initializing libiomp5.dylib, but found libomp.dylib already initialized." (OpenMP library conflict due to conda's MKL)

.vsts-ci.yml

@@ -122,7 +122,7 @@ jobs:
     displayName: Enable conda
   - script: |
       conda update -q -y conda
-      conda create -q -y -n %CONDA_ENV% python=%PYTHON_VERSION% matplotlib nose numpy pandas psutil pytest python-graphviz scikit-learn scipy
+      conda create -q -y -n %CONDA_ENV% python=%PYTHON_VERSION% matplotlib numpy pandas psutil pytest python-graphviz scikit-learn scipy
       cmd /c "activate %CONDA_ENV% & powershell -ExecutionPolicy Bypass -File %BUILD_SOURCESDIRECTORY%/.ci/test_windows.ps1"
     displayName: Test
   - task: PublishBuildArtifacts@1