HPCC-27343 apt-get install failing

Added missing apt-get update

Signed-off-by: Gordon Smith <GordonJSmith@gmail.com>

.github/workflows/build-vcpkg.yml

@@ -76,6 +76,7 @@ jobs:
         if: ${{ matrix.os == 'ubuntu-20.04' }}
         shell: "bash"
         run: |
+          sudo apt-get update -y
           sudo apt-get -yq install bison flex build-essential binutils-dev libldap2-dev libcppunit-dev libicu-dev libxslt1-dev \
             zlib1g-dev libboost-regex-dev libarchive-dev libv8-dev default-jdk libapr1-dev libaprutil1-dev libiberty-dev \
             libhiredis-dev libtbb-dev libxalan-c-dev libnuma-dev libevent-dev libatlas-base-dev libblas-dev python3-dev \