Remove caller option check

Babel 7.12+ supports .caller options

src/injectCaller.js

@@ -1,8 +1,4 @@
-const babel = require("@babel/core");
-
 module.exports = function injectCaller(opts, target) {
-  if (!supportsCallerOption()) return opts;
-
   return Object.assign({}, opts, {
     caller: Object.assign(
       {
@@ -25,26 +21,3 @@ module.exports = function injectCaller(opts, target) {
     ),
   });
 };
-
-// TODO: We can remove this eventually, I'm just adding it so that people have
-// a little time to migrate to the newer RCs of @babel/core without getting
-// hard-to-diagnose errors about unknown 'caller' options.
-let supportsCallerOptionFlag = undefined;
-function supportsCallerOption() {
-  if (supportsCallerOptionFlag === undefined) {
-    try {
-      // Rather than try to match the Babel version, we just see if it throws
-      // when passed a 'caller' flag, and use that to decide if it is supported.
-      babel.loadPartialConfig({
-        caller: undefined,
-        babelrc: false,
-        configFile: false,
-      });
-      supportsCallerOptionFlag = true;
-    } catch (err) {
-      supportsCallerOptionFlag = false;
-    }
-  }
-
-  return supportsCallerOptionFlag;
-}