fix: prune should omit descriptors from peerDependencies (#2269)

Partially addresses #2049 

Yarn 2+ doesn't expect descriptors that appear in `peerDependencies` to be kept. This behavior only manifested in a lockfile where a pruned package had a normal dependency descriptor that also appeared as a peer dependency descriptor in a package that wasn't pruned. As background "descriptor" is the term Yarn uses for a semver range that appears in a `package.json` or lockfile entry.

Amended the minimal berry lockfile to now test that we don't keep around descriptors even if they appear in `peerDependencies`.

cli/internal/lockfile/berry_lockfile.go

@@ -60,9 +60,6 @@ func (b *BerryLockfileEntry) possibleDescriptors() []_Descriptor {
 	for dep, version := range b.Dependencies {
 		addDescriptor(dep, version)
 	}
-	for dep, version := range b.PeerDependencies {
-		addDescriptor(dep, version)
-	}
 
 	return descriptors
 }

cli/internal/lockfile/testdata/minimal-berry.lock

@@ -11,6 +11,8 @@ __metadata:
   dependencies:
     c: "*"
     lodash: ^4.17.0
+  peerDependencies:
+    lodash: ^3.0.0 || ^4.0.0
   languageName: unknown
   linkType: soft