remove travis ci arm32 (#3279)

.travis.yml

@@ -31,15 +31,6 @@ matrix:
         - NAME=linux-clang
         - BUILD="mkdir build && cd build && cmake -DNCNN_BUILD_TESTS=ON .. && make -j2 && ctest --output-on-failure -j 2"
 
-    - name: "linux-gcc-arm32"
-      os: linux
-      arch: arm64
-      dist: bionic
-      env:
-        - NAME=linux-gcc-arm32
-        - BEFORE_BUILD="sudo apt-get update && sudo dpkg --add-architecture armhf && sudo rm /etc/apt/sources.list.d/mongodb*.list && sudo apt-get update && sudo apt-get -y install crossbuild-essential-armhf libc6:armhf libstdc++-5-dev:armhf linux-libc-dev:armhf"
-        - BUILD="mkdir build && cd build && cmake -DCMAKE_TOOLCHAIN_FILE=../toolchains/arm-linux-gnueabihf.toolchain.cmake -DNCNN_BUILD_TOOLS=OFF -DNCNN_BUILD_EXAMPLES=OFF - -DNCNN_BUILD_TESTS=ON .. && make -j2 VERBOSE=1 && ctest --output-on-failure -j 2"
-
 before_install:
   - eval "${BEFORE_BUILD}"