gnu: curl: Use hidden-package for curl's libssh2.

This is a followup to commits c1f4e6491c
and af8f7eb4f2.

* gnu/packages/curl.scm (libssh2-1.8.0): Use hidden-package.

gnu/packages/curl.scm

@@ -50,20 +50,21 @@
 
 ;; XXX A hidden special obsolete libssh2 for temporary use in the curl package.
 ;; <https://bugs.gnu.org/34927>
-(define libssh2-1.8.0
-  (package
-    (inherit libssh2)
-    (version "1.8.0")
-    (source (origin
-              (method url-fetch)
-              (uri (string-append
-                    "https://www.libssh2.org/download/libssh2-"
-                    version ".tar.gz"))
-               (sha256
-                (base32
-                 "1m3n8spv79qhjq4yi0wgly5s5rc8783jb1pyra9bkx1md0plxwrr"))
-               (patches
-                (search-patches "libssh2-fix-build-failure-with-gcrypt.patch"))))))
+(define-public libssh2-1.8.0
+  (hidden-package
+    (package
+      (inherit libssh2)
+      (version "1.8.0")
+      (source (origin
+                (method url-fetch)
+                (uri (string-append
+                      "https://www.libssh2.org/download/libssh2-"
+                      version ".tar.gz"))
+                (sha256
+                 (base32
+                  "1m3n8spv79qhjq4yi0wgly5s5rc8783jb1pyra9bkx1md0plxwrr"))
+                (patches
+                 (search-patches "libssh2-fix-build-failure-with-gcrypt.patch")))))))
 
 (define-public curl
   (package