Core: Stop removing AuctionRequest.video.plcmt during OpenRTB downgrade

src/main/java/org/prebid/server/auction/versionconverter/down/BidRequestOrtb26To25Converter.java

@@ -155,8 +155,7 @@ private static Video modifyVideo(Video video) {
                 video.getPodseq(),
                 video.getRqddurs(),
                 video.getSlotinpod(),
-                video.getMincpmpersec(),
-                video.getPlcmt())
+                video.getMincpmpersec())
 
                 ? video.toBuilder()
                 .maxseq(null)
@@ -166,7 +165,6 @@ private static Video modifyVideo(Video video) {
                 .rqddurs(null)
                 .slotinpod(null)
                 .mincpmpersec(null)
-                .plcmt(null)
                 .build()
 
                 : null;

src/test/groovy/org/prebid/server/functional/tests/OrtbConverterSpec.groovy

@@ -586,8 +586,9 @@ class OrtbConverterSpec extends BaseSpec {
         }
     }
 
-    def "PBS should remove imp[0].video.* when we don't support ortb 2.6"() {
+    def "PBS should remove imp[0].video.* and keep imp[0].video.plcmt when we don't support ortb 2.6"() {
         given: "Default bid request with imp[0].video.*"
+        def placement = PBSUtils.getRandomEnum(VideoPlcmtSubtype)
         def bidRequest = BidRequest.defaultBidRequest.tap {
             imp[0].video = Video.defaultVideo.tap {
                 rqddurs = [PBSUtils.randomNumber]
@@ -597,24 +598,27 @@ class OrtbConverterSpec extends BaseSpec {
                 podseq = PBSUtils.randomNumber
                 mincpmpersec = PBSUtils.randomDecimal
                 slotinpod = PBSUtils.randomNumber
-                plcmt = PBSUtils.getRandomEnum(VideoPlcmtSubtype)
+                plcmt = placement
             }
         }
 
         when: "Requesting PBS auction with ortb 2.5"
         prebidServerServiceWithElderOrtb.sendAuctionRequest(bidRequest)
 
-        then: "BidResponse shouldn't contain the imp[0].video.* as on request"
-        verifyAll(bidder.getBidderRequest(bidRequest.id)) {
+        then: "Bidder request shouldn't contain the imp[0].video.* as on request"
+        def bidderRequest = bidder.getBidderRequest(bidRequest.id)
+        verifyAll(bidderRequest) {
             !imp[0].video.rqddurs
             !imp[0].video.maxseq
             !imp[0].video.poddur
             !imp[0].video.podid
             !imp[0].video.podseq
             !imp[0].video.mincpmpersec
             !imp[0].video.slotinpod
-            !imp[0].video.plcmt
         }
+
+        and: "Bidder request should contain the imp[0].video.* as on request"
+        bidderRequest.imp[0].video.plcmt == placement
     }
 
     def "PBS shouldn't remove imp[0].video.* when we support ortb 2.6"() {

src/test/java/org/prebid/server/auction/versionconverter/down/BidRequestOrtb26To25ConverterTest.java

@@ -209,7 +209,6 @@ public void convertShouldRemoveFieldsThatAreNotInOrtb25() {
                                 .rqddurs(singletonList(1))
                                 .slotinpod(1)
                                 .mincpmpersec(BigDecimal.ONE)
-                                .plcmt(1)
                                 .build())
                         .audio(Audio.builder()
                                 .poddur(1)