fixed: add:sibling pkg refs leaked via git hook

`@telamonian/theme-darcula` is a package I've added to my source tree using `add:sibling`. I manually removed mentions of it before I committed changes to `package.json`, but it looks like they got re-added by the `jlpm run integrity` call that the `git push` hook performs.

dev_mode/package.json

@@ -96,7 +96,6 @@
     "@phosphor/signaling": "^1.2.2",
     "@phosphor/virtualdom": "^1.1.2",
     "@phosphor/widgets": "^1.6.0",
-    "@telamonian/theme-darcula": "^1.0.0-alpha.3",
     "ajv": "^6.5.5",
     "codemirror": "~5.42.0",
     "comment-json": "^1.1.3",
@@ -170,7 +169,6 @@
       "@jupyterlab/statusbar-extension": "",
       "@jupyterlab/tabmanager-extension": "",
       "@jupyterlab/terminal-extension": "",
-      "@telamonian/theme-darcula": "",
       "@jupyterlab/theme-dark-extension": "",
       "@jupyterlab/theme-light-extension": "",
       "@jupyterlab/tooltip-extension": ""
@@ -300,7 +298,6 @@
       "@jupyterlab/tabmanager-extension": "../packages/tabmanager-extension",
       "@jupyterlab/terminal": "../packages/terminal",
       "@jupyterlab/terminal-extension": "../packages/terminal-extension",
-      "@telamonian/theme-darcula": "../packages/theme-darcula",
       "@jupyterlab/theme-dark-extension": "../packages/theme-dark-extension",
       "@jupyterlab/theme-light-extension": "../packages/theme-light-extension",
       "@jupyterlab/tooltip": "../packages/tooltip",