ci: Fix builds manifests

Remove `.git` suffix from river repo in `sources` section as the
suffix make the ci only clone the repo. Without the suffix the ci
checkout the correct commit to build river.

We don't need to remove the suffix from others sources as cloning
the repo and checkout the tag version we want is enough.

.builds/alpine.yml

@@ -20,9 +20,9 @@ packages:
   - wget
   - xz
 sources:
+  - https://github.com/riverwm/river
   - https://gitlab.freedesktop.org/wayland/wayland.git
   - https://gitlab.freedesktop.org/wlroots/wlroots.git
-  - https://github.com/riverwm/river.git
 tasks:
   - install_deps: |
       cd wayland

.builds/archlinux.yml

@@ -17,9 +17,9 @@ packages:
   - wget
   - xz
 sources:
+  - https://github.com/riverwm/river
   - https://gitlab.freedesktop.org/wayland/wayland.git
   - https://gitlab.freedesktop.org/wlroots/wlroots.git
-  - https://github.com/riverwm/river.git
 tasks:
   - install_deps: |
       cd wayland

.builds/freebsd.yml

@@ -21,9 +21,9 @@ packages:
   - scdoc
   - wget
 sources:
+  - https://github.com/riverwm/river
   - https://gitlab.freedesktop.org/wayland/wayland.git
   - https://gitlab.freedesktop.org/wlroots/wlroots.git
-  - https://github.com/riverwm/river.git
 tasks:
   - install_deps: |
       cd wayland