docker: remove libcap development packages

Libcap was dropped from virtio-9p (commit 7e46261368), so remove it from
the dockerfiles as well.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Acked-by: Alex Bennée <alex.bennee@linaro.org>
[groug, mention SHA1 that dropped libcap]
Signed-off-by: Greg Kurz <groug@kaod.org>

tests/docker/dockerfiles/fedora.docker

@@ -25,7 +25,6 @@ ENV PACKAGES \
     libasan \
     libattr-devel \
     libblockdev-mpath-devel \
-    libcap-devel \
     libcap-ng-devel \
     libcurl-devel \
     libfdt-devel \

tests/docker/dockerfiles/ubuntu.docker

@@ -23,7 +23,6 @@ ENV PACKAGES flex bison \
     libbrlapi-dev \
     libbz2-dev \
     libcacard-dev \
-    libcap-dev \
     libcap-ng-dev \
     libcurl4-gnutls-dev \
     libdrm-dev \

tests/docker/dockerfiles/ubuntu1804.docker

@@ -12,7 +12,6 @@ ENV PACKAGES flex bison \
     libbrlapi-dev \
     libbz2-dev \
     libcacard-dev \
-    libcap-dev \
     libcap-ng-dev \
     libcurl4-gnutls-dev \
     libdrm-dev \