Remove tabmanager from dev_mode.

dev_mode/imports.css

@@ -31,7 +31,6 @@
 @import url('~@jupyterlab/running-extension/style/index.css');
 @import url('~@jupyterlab/settingeditor-extension/style/index.css');
 @import url('~@jupyterlab/statusbar-extension/style/index.css');
-@import url('~@jupyterlab/tabmanager-extension/style/index.css');
 @import url('~@jupyterlab/terminal-extension/style/index.css');
 @import url('~@jupyterlab/toc-extension/style/index.css');
 @import url('~@jupyterlab/tooltip-extension/style/index.css');

dev_mode/package.json

@@ -155,7 +155,6 @@
     "@jupyterlab/settingeditor-extension": "~3.0.0-beta.4",
     "@jupyterlab/shortcuts-extension": "~3.0.0-beta.4",
     "@jupyterlab/statusbar-extension": "~3.0.0-beta.4",
-    "@jupyterlab/tabmanager-extension": "~3.0.0-beta.4",
     "@jupyterlab/terminal-extension": "~3.0.0-beta.4",
     "@jupyterlab/theme-dark-extension": "~3.0.0-beta.4",
     "@jupyterlab/theme-light-extension": "~3.0.0-beta.4",
@@ -232,7 +231,6 @@
       "@jupyterlab/settingeditor-extension": "",
       "@jupyterlab/shortcuts-extension": "",
       "@jupyterlab/statusbar-extension": "",
-      "@jupyterlab/tabmanager-extension": "",
       "@jupyterlab/terminal-extension": "",
       "@jupyterlab/theme-dark-extension": "",
       "@jupyterlab/theme-light-extension": "",
@@ -371,7 +369,6 @@
       "@jupyterlab/statedb": "../packages/statedb",
       "@jupyterlab/statusbar": "../packages/statusbar",
       "@jupyterlab/statusbar-extension": "../packages/statusbar-extension",
-      "@jupyterlab/tabmanager-extension": "../packages/tabmanager-extension",
       "@jupyterlab/terminal": "../packages/terminal",
       "@jupyterlab/terminal-extension": "../packages/terminal-extension",
       "@jupyterlab/theme-dark-extension": "../packages/theme-dark-extension",