Update skip versions for flat_object tests (opensearch-project#15448)

While fixing a flat_object bug, I noticed that we were skipping all
related yamlRestTests on pre-3.0 versions. Since the flat object field
type was added in 2.7, that should be the correct skip level for most
tests. The bug I fixed is still present in 2.16 and earlier, so the
test that covers that fix needs to be skipped pre-2.17.

Signed-off-by: Michael Froh <[email protected]>

Author: msfroh

rest-api-spec/src/main/resources/rest-api-spec/test/index/100_partial_flat_object.yml

@@ -114,8 +114,8 @@ teardown:
 # and no dynamic fields were created.
 "Mappings":
   - skip:
-      version: " - 2.99.99"
-      reason: "flat_object is introduced in 3.0.0 in main branch"
+      version: " - 2.16.99"
+      reason: "flat_object field with null (doc 4) throws exception before 2.17"
 
   - do:
       indices.get_mapping:
@@ -131,8 +131,8 @@ teardown:
 ---
 "Supported queries":
   - skip:
-      version: " - 2.99.99"
-      reason: "flat_object is introduced in 3.0.0 in main branch"
+      version: " - 2.16.99"
+      reason: "flat_object field with null (doc 4) throws exception before 2.17"
 
 
   # Verify Document Count

rest-api-spec/src/main/resources/rest-api-spec/test/index/105_partial_flat_object_nested.yml

@@ -89,8 +89,8 @@ teardown:
 # and no dynamic fields were created.
 "Mappings":
   - skip:
-      version: " - 2.99.99"
-      reason: "flat_object is introduced in 3.0.0 in main branch"
+      version: " - 2.6.99"
+      reason: "flat_object is introduced in 2.7"
 
   - do:
       indices.get_mapping:
@@ -106,8 +106,8 @@ teardown:
 ---
 "Supported queries":
   - skip:
-      version: " - 2.99.99"
-      reason: "flat_object is introduced in 3.0.0 in main branch"
+      version: " - 2.6.99"
+      reason: "flat_object is introduced in 2.7"
 
 
   # Verify Document Count

rest-api-spec/src/main/resources/rest-api-spec/test/index/90_flat_object.yml

@@ -97,8 +97,8 @@ teardown:
 ---
 "Supported queries":
   - skip:
-      version: " - 2.99.99"
-      reason: "flat_object is introduced in 3.0.0 in main branch"
+      version: " - 2.6.99"
+      reason: "flat_object is introduced in 2.7"
 
   # Verify Document Count
   - do:
@@ -607,8 +607,8 @@ teardown:
 ---
 "Unsupported":
   - skip:
-      version: " - 2.99.99"
-      reason: "flat_object is introduced in 3.0.0 in main branch"
+      version: " - 2.6.99"
+      reason: "flat_object is introduced in 2.7"
 
   # Mapping parameters (such as index/search analyzers) are currently not supported
   # The plan is to support them in the next version