Fix static property falling through in declare class Flow AST

[danharper]

Given the following:

declare class X {
    a: number;
    static b: number;
    c: number;
}

c would get marked as static as it's not being reset between properties.

https://astexplorer.net/#/4Bi9Ce53LA

[codecov-io]

Current coverage is 94.39% (diff: 100%)

Merging #135 into master will increase coverage by <.01%

@@             master       #135   diff @@
==========================================
  Files            19         19          
  Lines          3082       3084     +2   
  Methods         325        325          
  Messages          0          0          
  Branches        806        806          
==========================================
+ Hits           2909       2911     +2   
  Misses           94         94          
  Partials         79         79          

Powered by Codecov. Last update 9cb73d8...2f953de

[danez]

Awesome thanks