Modify skips for get missing alises tests

Previous work modified the status code on the get aliases API when an
alias is missing so that these requests 404 now. This change was also
backported to 5.5 so we can adjust the skips to skip everything before
5.5.0.

rest-api-spec/src/main/resources/rest-api-spec/test/indices.delete_alias/10_basic.yml

@@ -1,7 +1,7 @@
 ---
 "Basic test for delete alias":
   - skip:
-      version: " - 5.99.99"
+      version: " - 5.4.99"
       reason: Previous versions did not 404 on missing aliases
 
   - do:

rest-api-spec/src/main/resources/rest-api-spec/test/indices.get_alias/10_basic.yml

@@ -167,7 +167,7 @@ setup:
 ---
 "Non-existent alias on an existing index returns 404":
   - skip:
-      version: " - 5.99.99"
+      version: " - 5.4.99"
       reason: Previous versions did not 404 on missing aliases
 
   - do:
@@ -182,7 +182,7 @@ setup:
 ---
 "Existent and non-existent alias returns 404 and the existing alias":
   - skip:
-      version: " - 5.99.99"
+      version: " - 5.4.99"
       reason: Previous versions did not 404 on missing aliases
 
   - do:
@@ -198,7 +198,7 @@ setup:
 ---
 "Existent and non-existent aliases returns 404 and the existing alias":
   - skip:
-      version: " - 5.99.99"
+      version: " - 5.4.99"
       reason: Previous versions did not 404 on missing aliases
 
   - do: