update requires to use list; remove field (#1234)

syft/pkg/cataloger/cpp/parse_conanlock.go

@@ -20,8 +20,7 @@ type conanLock struct {
 			PackageID      string   `json:"package_id"`
 			Context        string   `json:"context"`
 			Prev           string   `json:"prev"`
-			Requires       string `json:"requires"`
-			BuildRequires  string `json:"build_requires"`
+			Requires       []string `json:"requires"`
 			PythonRequires string   `json:"py_requires"`
 			Options        string   `json:"options"`
 			Path           string   `json:"path"`

syft/pkg/cataloger/cpp/test-fixtures/conan.lock

@@ -4,6 +4,7 @@
    "0": {
     "ref": "zlib/1.2.12",
     "options": "fPIC=True\nshared=False",
+    "requires": [],
     "path": "all/conanfile.py",
     "context": "host"
    }