Delete never-implemented CSP “navigate-to” directive

See w3c/webappsec-csp#564. The
“navigate-to” directive was removed from the CSP spec and no
implementation of it ever shipped anywhere.

Related MDN change: mdn/content#21147

http/headers/Content-Security-Policy.json

@@ -628,40 +628,6 @@
             }
           }
         },
-        "navigate-to": {
-          "__compat": {
-            "mdn_url": "https://developer.mozilla.org/docs/Web/HTTP/Headers/Content-Security-Policy/navigate-to",
-            "spec_url": "https://w3c.github.io/webappsec-csp/#directive-navigate-to",
-            "support": {
-              "chrome": {
-                "version_added": false
-              },
-              "chrome_android": "mirror",
-              "edge": "mirror",
-              "firefox": {
-                "version_added": false
-              },
-              "firefox_android": "mirror",
-              "ie": {
-                "version_added": false
-              },
-              "oculus": "mirror",
-              "opera": "mirror",
-              "opera_android": "mirror",
-              "safari": {
-                "version_added": false
-              },
-              "safari_ios": "mirror",
-              "samsunginternet_android": "mirror",
-              "webview_android": "mirror"
-            },
-            "status": {
-              "experimental": true,
-              "standard_track": true,
-              "deprecated": false
-            }
-          }
-        },
         "object-src": {
           "__compat": {
             "mdn_url": "https://developer.mozilla.org/docs/Web/HTTP/Headers/Content-Security-Policy/object-src",