[TEST] Adjust version skips for movavg/movfn tests

Since the MovFn PR was backported to 6.x, we can adjust
the version skip numbers in master to correctly
match 6.3.99 instead of 6.4.0

modules/lang-painless/src/test/resources/rest-api-spec/test/painless/70_mov_fn_agg.yml

@@ -2,7 +2,7 @@
 #
 setup:
   - skip:
-        version: " - 6.4.0"
+        version: " - 6.3.99"
         reason:  "moving_fn added in 6.4.0"
   - do:
       indices.create:

rest-api-spec/src/main/resources/rest-api-spec/test/search.aggregation/250_moving_fn.yml

@@ -1,6 +1,6 @@
 setup:
   - skip:
-        version: " - 6.4.0"
+        version: " - 6.3.99"
         reason:  "moving_fn added in 6.4.0"
 
 ---

rest-api-spec/src/main/resources/rest-api-spec/test/search.aggregation/80_typed_keys.yml

@@ -197,7 +197,7 @@ setup:
 "Test typed keys parameter for date_histogram aggregation and max_bucket pipeline aggregation":
   - skip:
       features: warnings
-      version: " - 6.4.0"
+      version: " - 6.3.99"
       reason:  "deprecation added in 6.4.0"
   - do:
       warnings: