spec: fix crystalball map js build

why:
- Our build is currently broken due to some config additions I made to
  enable HMR.
- We'll only enable the react refresh config in dev when we're not
  trying to build coverage.

flag=none

test-plan:
- You can run `CRYSTALBALL_MAP=1 yarn build:js` locally without error.
- The failing build passes.

Change-Id: I89a79d576632a4169239f2ef6115d9bc0c2a5795
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/352625
Tested-by: Service Cloud Jenkins <svc.cloudjenkins@instructure.com>
Reviewed-by: James Butters <jbutters@instructure.com>
QA-Review: Ryan Hawkins <ryan.hawkins@instructure.com>
Product-Review: Ryan Hawkins <ryan.hawkins@instructure.com>

ui-build/webpack/webpack.rules.js

@@ -139,12 +139,19 @@ exports.swc = [
         env: {
           targets: browserTargets,
         },
-        transform: {
-          react: {
-            development: process.env.NODE_ENV === 'development',
-            refresh: process.env.NODE_ENV === 'development',
-          },
-        },
+        // Our coverage plugin gets really upset about the transform field, even
+        // if it's just react: {development: false, refresh: false}, so we only
+        // include it in development mode when crystalball is disabled.
+        ...(process.env.NODE_ENV === 'development' && !isCrystalballEnabled
+          ? {
+              transform: {
+                react: {
+                  development: process.env.NODE_ENV === 'development',
+                  refresh: process.env.NODE_ENV === 'development',
+                },
+              },
+            }
+          : {}),
       },
     },
   },