[ci] Revert fix recent conda and mamba matching error #7047 (#7049)

.ci/setup.sh

@@ -153,7 +153,7 @@ if [[ "${TASK}" != "cpp-tests" ]] && [[ "${TASK}" != "r-package" ]]; then
         sh miniforge.sh -b -p "${CONDA}"
     fi
     conda config --set always_yes yes --set changeps1 no
-    conda update -q -y conda conda-libmamba-solver
+    conda update -q -y conda
 
     # print output of 'conda info', to help in submitting bug reports
     echo "conda info:"

.ci/test-windows.ps1

@@ -66,7 +66,7 @@ if ($env:TASK -eq "swig") {
 conda init powershell
 conda activate
 conda config --set always_yes yes --set changeps1 no
-conda update -q -y conda conda-libmamba-solver "python=$env:PYTHON_VERSION[build=*_cp*]"
+conda update -q -y conda "python=$env:PYTHON_VERSION[build=*_cp*]"
 
 # print output of 'conda info', to help in submitting bug reports
 Write-Output "conda info:"

docs/build-docs.sh

@@ -14,7 +14,7 @@ curl \
 /bin/bash "${HOME}/miniforge.sh" -b -p "${CONDA}"
 
 conda config --set always_yes yes --set changeps1 no
-conda update -q -y conda conda-libmamba-solver
+conda update -q -y conda
 
 conda env create \
     --name docs-env \