Upgrade to Flow v0.50.0 (#10249)

No particular reason, just hoping memory usage is maybe better.

.flowconfig

@@ -38,4 +38,4 @@ suppress_comment=\\(.\\|\n\\)*\\$FlowFixedInNextDeploy
 suppress_comment=\\(.\\|\n\\)*\\$FlowExpectedError
 
 [version]
-^0.48.0
+^0.50.0

package.json

@@ -56,7 +56,7 @@
     "fbjs": "^0.8.9",
     "fbjs-scripts": "^0.6.0",
     "filesize": "^3.5.6",
-    "flow-bin": "^0.48.0",
+    "flow-bin": "^0.50.0",
     "git-branch": "^0.3.0",
     "glob": "^6.0.4",
     "glob-stream": "^6.1.0",

yarn.lock

@@ -2308,9 +2308,9 @@ flat-cache@^1.2.1:
     graceful-fs "^4.1.2"
     write "^0.2.1"
 
-flow-bin@^0.48.0:
-  version "0.48.0"
-  resolved "https://registry.yarnpkg.com/flow-bin/-/flow-bin-0.48.0.tgz#72d075143524358db8901525e3c784dc13a7c7ee"
+flow-bin@^0.50.0:
+  version "0.50.0"
+  resolved "https://registry.yarnpkg.com/flow-bin/-/flow-bin-0.50.0.tgz#d4cdb2430dee1a3599f0eb6fe551146e3027256a"
 
 flow-parser@0.43.0:
   version "0.43.0"