remove C# jessie x86 dockerfile

tools/dockerfile/distribtest/csharp_jessie_x86/Dockerfile

@@ -1,31 +0,0 @@
-# Copyright 2015 gRPC authors.
-#
-# Licensed under the Apache License, Version 2.0 (the "License");
-# you may not use this file except in compliance with the License.
-# You may obtain a copy of the License at
-#
-#     http://www.apache.org/licenses/LICENSE-2.0
-#
-# Unless required by applicable law or agreed to in writing, software
-# distributed under the License is distributed on an "AS IS" BASIS,
-# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-# See the License for the specific language governing permissions and
-# limitations under the License.
-
-FROM i386/debian:jessie
-
-RUN apt-get update && apt-get install -y apt-transport-https && apt-get clean
-
-RUN apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys 3FA7E0328081BFF6A14DA29AA6A19B38D3D831EF
-RUN echo "deb https://download.mono-project.com/repo/debian stable-jessie main" | tee /etc/apt/sources.list.d/mono-official-stable.list
-
-RUN apt-get update && apt-get install -y \
-    mono-devel \
-    nuget \
-    && apt-get clean
-
-RUN apt-get update && apt-get install -y unzip && apt-get clean
-
-# Make sure the mono certificate store is up-to-date to prevent issues with nuget restore
-RUN apt-get update && apt-get install -y curl && apt-get clean
-RUN curl https://curl.haxx.se/ca/cacert.pem > ~/cacert.pem && cert-sync ~/cacert.pem && rm -f ~/cacert.pem