fix(CocoaPods): Stop taking pure version constraints as dependencies

Second-level entries in the "PODS" section are just "pure" constraints
which should not be added as dependencies at all unless their names also
appear with resolved versions as first-level entries.

This partly reverts 18f9be2 which introduced this over-reporting by
unconditionally adding constraints as dependencies. However, that did
not surface until the test added in 4bbd26a.

Signed-off-by: Sebastian Schuberth <sschuberth@gmail.com>

plugins/package-managers/cocoapods/src/funTest/assets/projects/synthetic/external-sources-expected-output.yml

@@ -28,7 +28,6 @@ project:
       - id: "Pod::AFNetworking/Reachability:3.2.1"
       - id: "Pod::AFNetworking/Security:3.2.1"
       - id: "Pod::AFNetworking/Serialization:3.2.1"
-      - id: "Pod::AFNetworking/UIKit:3.2.1"
     - id: "Pod::CocoaSecurity:1.2.4"
     - id: "Pod::MLHudAlert:0.0.4-3f23fa41632f8935fed028b04335576633ec53a2"
     - id: "Pod::Ono:2.1.1"
@@ -173,34 +172,6 @@ packages:
     url: "https://github.com/AFNetworking/AFNetworking.git"
     revision: "3.2.1"
     path: ""
-- id: "Pod::AFNetworking/UIKit:3.2.1"
-  purl: "pkg:cocoapods/AFNetworking%2FUIKit@3.2.1"
-  declared_licenses:
-  - "MIT"
-  declared_licenses_processed:
-    spdx_expression: "MIT"
-  description: "A delightful iOS and OS X networking framework."
-  homepage_url: "https://github.com/AFNetworking/AFNetworking"
-  binary_artifact:
-    url: ""
-    hash:
-      value: ""
-      algorithm: ""
-  source_artifact:
-    url: ""
-    hash:
-      value: ""
-      algorithm: ""
-  vcs:
-    type: "Git"
-    url: "https://github.com/AFNetworking/AFNetworking.git"
-    revision: "3.2.1"
-    path: ""
-  vcs_processed:
-    type: "Git"
-    url: "https://github.com/AFNetworking/AFNetworking.git"
-    revision: "3.2.1"
-    path: ""
 - id: "Pod::CocoaSecurity:1.2.4"
   purl: "pkg:cocoapods/CocoaSecurity@1.2.4"
   declared_licenses: