Bump BWC versions after #25658 backport to 5.6

Author: s1monw

core/src/main/java/org/elasticsearch/action/search/SearchRequest.java

@@ -406,7 +406,7 @@ public void readFrom(StreamInput in) throws IOException {
         indicesOptions = IndicesOptions.readIndicesOptions(in);
         requestCache = in.readOptionalBoolean();
         batchedReduceSize = in.readVInt();
-        if (in.getVersion().onOrAfter(Version.V_6_0_0_beta1)) {
+        if (in.getVersion().onOrAfter(Version.V_5_6_0)) {
             maxConcurrentShardRequests = in.readVInt();
             preFilterShardSize = in.readVInt();
         }
@@ -428,7 +428,7 @@ public void writeTo(StreamOutput out) throws IOException {
         indicesOptions.writeIndicesOptions(out);
         out.writeOptionalBoolean(requestCache);
         out.writeVInt(batchedReduceSize);
-        if (out.getVersion().onOrAfter(Version.V_6_0_0_beta1)) {
+        if (out.getVersion().onOrAfter(Version.V_5_6_0)) {
             out.writeVInt(maxConcurrentShardRequests);
             out.writeVInt(preFilterShardSize);
         }

core/src/main/java/org/elasticsearch/action/search/SearchResponse.java

@@ -324,7 +324,7 @@ public void readFrom(StreamInput in) throws IOException {
         }
         scrollId = in.readOptionalString();
         tookInMillis = in.readVLong();
-        if (in.getVersion().onOrAfter(Version.V_6_0_0_beta1)) {
+        if (in.getVersion().onOrAfter(Version.V_5_6_0)) {
             skippedShards = in.readVInt();
         }
     }
@@ -343,7 +343,7 @@ public void writeTo(StreamOutput out) throws IOException {
 
         out.writeOptionalString(scrollId);
         out.writeVLong(tookInMillis);
-        if(out.getVersion().onOrAfter(Version.V_6_0_0_beta1)) {
+        if(out.getVersion().onOrAfter(Version.V_5_6_0)) {
             out.writeVInt(skippedShards);
         }
     }

rest-api-spec/src/main/resources/rest-api-spec/test/search/140_pre_filter_search_shards.yml

@@ -40,8 +40,8 @@ setup:
 ---
 "pre_filter_shard_size with invalid parameter":
   - skip:
-      version: " - 5.99.99"
-      reason:  this was added in 6.0.0
+      version: " - 5.5.99"
+      reason:  this was added in 5.6.0
   - do:
       catch: /preFilterShardSize must be >= 1/
       search:
@@ -51,8 +51,8 @@ setup:
 ---
 "pre_filter_shard_size with shards that have no hit":
   - skip:
-      version: " - 5.99.99"
-      reason:  this was added in 6.0.0
+      version: " - 5.5.99"
+      reason:  this was added in 5.6.0
   - do:
       index:
         index: index_1