Fix BWC for fileBasedRecovery flag removal (#45185)

Completes the backport of #45131, see also #45146.

build.gradle

@@ -173,8 +173,8 @@ task verifyVersions {
  * after the backport of the backcompat code is complete.
  */
 
-boolean bwc_tests_enabled = false
-final String bwc_tests_disabled_issue = "https://github.com/elastic/elasticsearch/pull/45146" /* place a PR link here when committing bwc changes */
+boolean bwc_tests_enabled = true
+final String bwc_tests_disabled_issue = "" /* place a PR link here when committing bwc changes */
 if (bwc_tests_enabled == false) {
   if (bwc_tests_disabled_issue.isEmpty()) {
     throw new GradleException("bwc_tests_disabled_issue must be set when bwc_tests_enabled == false")

server/src/main/java/org/elasticsearch/indices/recovery/RecoveryPrepareForTranslogOperationsRequest.java

@@ -44,7 +44,7 @@ class RecoveryPrepareForTranslogOperationsRequest extends TransportRequest {
         recoveryId = in.readLong();
         shardId = new ShardId(in);
         totalTranslogOps = in.readVInt();
-        if (in.getVersion().before(Version.V_8_0_0)) {
+        if (in.getVersion().before(Version.V_7_4_0)) {
             in.readBoolean(); // was fileBasedRecovery
         }
     }
@@ -67,7 +67,7 @@ class RecoveryPrepareForTranslogOperationsRequest extends TransportRequest {
         out.writeLong(recoveryId);
         shardId.writeTo(out);
         out.writeVInt(totalTranslogOps);
-        if (out.getVersion().before(Version.V_8_0_0)) {
+        if (out.getVersion().before(Version.V_7_4_0)) {
             out.writeBoolean(true); // was fileBasedRecovery
         }
     }