GH-48572: [CI] Remove centos-7-cpp dockerfile and reference from compose (#48573)

### Rationale for this change

After #45449 was done this docker file is not used anymore.

### What changes are included in this PR?

Remove unused dockerfile after dropping support for centos-7 packaging and remove R builds for OpenSSL 1.x

### Are these changes tested?

No

### Are there any user-facing changes?

No

* GitHub Issue: #48572

Authored-by: Raúl Cumplido <[email protected]>
Signed-off-by: Sutou Kouhei <[email protected]>

Author: raulcd

ci/docker/centos-7-cpp.dockerfile

@@ -115,7 +115,6 @@ x-hierarchy:
   - almalinux-verify-rc
   - alpine-linux-cpp
   - alpine-linux-r
-  - centos-cpp-static
   - conda:
     - conda-cpp:
       - conda-integration
@@ -448,26 +447,6 @@ services:
         cd /arrow &&
         r/inst/build_arrow_static.sh"
 
-  centos-cpp-static:
-    image: ${REPO}:centos-7-cpp-static
-    build:
-      context: .
-      dockerfile: ci/docker/centos-7-cpp.dockerfile
-      cache_from:
-        - ${REPO}:centos-7-cpp-static
-      args:
-        cmake: ${CMAKE}
-    shm_size: *shm-size
-    volumes:
-      - .:/arrow:delegated
-    environment:
-      <<: [*common, *ccache, *sccache, *cpp]
-      ARROW_DEPENDENCY_SOURCE: BUNDLED
-      ARROW_HOME: /arrow
-      LIBARROW_MINIMAL: "false"
-    command: /bin/bash -c "
-          scl enable devtoolset-8 '/arrow/r/inst/build_arrow_static.sh'"
-
   ubuntu-cpp-bundled:
     # Arrow build with BUNDLED dependencies
     image: ${REPO}:${ARCH}-ubuntu-${UBUNTU}-cpp-minimal