chore: remove gitHead field from package.json

It was introduced only due to a failed `lerna publish`

packages/@vue/cli-plugin-babel/package.json

@@ -28,6 +28,5 @@
   },
   "publishConfig": {
     "access": "public"
-  },
-  "gitHead": "0dc793497281718762a5477a3de4a7ee439cdda6"
+  }
 }

packages/@vue/cli-plugin-typescript/package.json

@@ -41,6 +41,5 @@
     "typescript": "^3.4.3",
     "vue-class-component": "^7.0.2",
     "vue-property-decorator": "^8.1.0"
-  },
-  "gitHead": "0dc793497281718762a5477a3de4a7ee439cdda6"
+  }
 }

packages/@vue/cli-plugin-unit-jest/package.json

@@ -35,6 +35,5 @@
   "devDependencies": {
     "@vue/test-utils": "1.0.0-beta.29",
     "ts-jest": "^23.0.0"
-  },
-  "gitHead": "0dc793497281718762a5477a3de4a7ee439cdda6"
+  }
 }

packages/@vue/cli-service-global/package.json

@@ -33,6 +33,5 @@
     "resolve": "^1.10.0",
     "vue": "^2.6.10",
     "vue-template-compiler": "^2.6.10"
-  },
-  "gitHead": "0dc793497281718762a5477a3de4a7ee439cdda6"
+  }
 }

packages/@vue/cli-service/package.json

@@ -97,6 +97,5 @@
   },
   "engines": {
     "node": ">=8"
-  },
-  "gitHead": "0dc793497281718762a5477a3de4a7ee439cdda6"
+  }
 }

packages/@vue/cli-ui-addon-webpack/package.json

@@ -35,6 +35,5 @@
   ],
   "publishConfig": {
     "access": "public"
-  },
-  "gitHead": "0dc793497281718762a5477a3de4a7ee439cdda6"
+  }
 }

packages/@vue/cli-ui-addon-widgets/package.json

@@ -29,6 +29,5 @@
   },
   "publishConfig": {
     "access": "public"
-  },
-  "gitHead": "0dc793497281718762a5477a3de4a7ee439cdda6"
+  }
 }

packages/@vue/cli-ui/package.json

@@ -126,6 +126,5 @@
     "ui": [
       "ui-dev.js"
     ]
-  },
-  "gitHead": "0dc793497281718762a5477a3de4a7ee439cdda6"
+  }
 }

packages/@vue/cli/package.json

@@ -60,6 +60,5 @@
   },
   "engines": {
     "node": ">=8.9"
-  },
-  "gitHead": "0dc793497281718762a5477a3de4a7ee439cdda6"
+  }
 }