ci: Require gtk3-devel instead of gtk2-devel

Ref: 01c9a51c70
Signed-off-by: Michael Vetter <jubalh@iodoru.org>

ci/Dockerfile.fedora

@@ -11,7 +11,7 @@ RUN dnf install -y \
   git \
   glib2-devel \
   glibc-all-langpacks \
-  gtk2-devel \
+  gtk3-devel \
   libXScrnSaver-devel \
   libcmocka-devel \
   libcurl-devel \

ci/Dockerfile.ubuntu

@@ -13,7 +13,7 @@ RUN apt-get update && apt-get install -y --no-install-recommends \
   libgcrypt-dev \
   libglib2.0-dev \
   libgpgme11-dev \
-  libgtk2.0-dev \
+  libgtk-3-dev \
   libncursesw5-dev \
   libnotify-dev \
   libotr5-dev \