fix(NODE-7512): set CLIENT_ENCRYPTION expansion for Windows node-latest variant

The node-latest smoke test build variant was missing CLIENT_ENCRYPTION from
its expansions when clientEncryption is false (as it is on Windows per NODE-3401).
run-tests.sh requires the var to be exactly "true" or "false" and exits 1
otherwise, causing all Windows node-latest tasks to fail before any tests run.

Align with the regular variant loop by always emitting String(!!clientEncryption)
instead of conditionally setting it only when truthy.

Author: tadjik1

.evergreen/config.yml

@@ -3687,7 +3687,8 @@ buildvariants:
     run_on: rhel80-large
     expansions:
       NODE_LTS_VERSION: latest
-      CLIENT_ENCRYPTION: true
+      CLIENT_ENCRYPTION: 'true'
+      TEST_CSFLE: 'true'
     tasks:
       - test-latest-server
       - test-latest-replica_set
@@ -3873,6 +3874,8 @@ buildvariants:
     run_on: windows-2022-latest-large
     expansions:
       NODE_LTS_VERSION: latest
+      CLIENT_ENCRYPTION: 'false'
+      TEST_CSFLE: 'false'
     tasks:
       - test-latest-server
       - test-latest-replica_set

.evergreen/generate_evergreen_tasks.js

@@ -424,12 +424,13 @@ for (const {
       name: `${osName}-node-latest`,
       display_name: `${osDisplayName} Node Latest`,
       run_on,
-      expansions: { NODE_LTS_VERSION: 'latest' },
+      expansions: {
+        NODE_LTS_VERSION: 'latest',
+        CLIENT_ENCRYPTION: String(!!clientEncryption),
+        TEST_CSFLE: String(!!clientEncryption)
+      },
       tasks: tasks.map(({ name }) => name)
     };
-    if (clientEncryption) {
-      buildVariantData.expansions.CLIENT_ENCRYPTION = true;
-    }
     BUILD_VARIANTS.push(buildVariantData);
   }
 }