Packaging: add arm7 platform in the main pipeline (#26575) (#26599)

(cherry picked from commit ef283a8)

Co-authored-by: Victor Martinez <victormartinezrubio@gmail.com>

Jenkinsfile

@@ -352,9 +352,9 @@ def packagingLinux(Map args = [:]) {
                 'linux/amd64',
                 'linux/386',
                 'linux/arm64',
+                'linux/armv7',
                 // The platforms above are disabled temporarly as crossbuild images are
                 // not available. See: https://github.com/elastic/golang-crossbuild/issues/71
-                //'linux/armv7',
                 //'linux/ppc64le',
                 //'linux/mips64',
                 //'linux/s390x',