lib: remove an unnecessary coverage check

PR-URL: https://github.com/nodejs/node/pull/12023
Fixes: https://github.com/nodejs/node/issues/11445
Refs: f65a48fc8f
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Franziska Hinkelmann <franziska.hinkelmann@gmail.com>

lib/internal/process/write-coverage.js

@@ -5,12 +5,10 @@ const fs = require('fs');
 const mkdirSync = fs.mkdirSync;
 const writeFileSync = fs.writeFileSync;
 
-var isWritingCoverage = false;
 function writeCoverage() {
-  if (isWritingCoverage || !global.__coverage__) {
+  if (!global.__coverage__) {
     return;
   }
-  isWritingCoverage = true;
 
   const dirname = path.join(path.dirname(process.execPath), '.coverage');
   const filename = `coverage-${process.pid}-${Date.now()}.json`;