[MINOR] Move to using standard DISCLAIMER (#6565)

### What changes were proposed in this pull request?

Use standard disclaimer text and file name.

### Why are the changes needed?

To comply with ASF policy.

Fix: #(issue)

### Does this PR introduce _any_ user-facing change?

No.

### How was this patch tested?

N/A

DISCLAIMER.txt

@@ -0,0 +1 @@
+Apache Gravitino is an effort undergoing incubation at The Apache Software Foundation (ASF), sponsored by the ASF Incubator. Incubation is required of all newly accepted projects until a further review indicates that the infrastructure, communications, and decision making process have stabilized in a manner consistent with other successful ASF projects. While incubation status is not necessarily a reflection of the completeness or stability of the code, it does indicate that the project has yet to be fully endorsed by the ASF.

build.gradle.kts

@@ -621,7 +621,7 @@ tasks {
         from(projectDir.file("LICENSE.bin")) { into("package") }
         from(projectDir.file("NOTICE.bin")) { into("package") }
         from(projectDir.file("README.md")) { into("package") }
-        from(projectDir.file("DISCLAIMER_WIP.txt")) { into("package") }
+        from(projectDir.file("DISCLAIMER.txt")) { into("package") }
         into(outputDir)
         rename { fileName ->
           fileName.replace(".bin", "")
@@ -667,7 +667,7 @@ tasks {
         from(projectDir.file("LICENSE.rest")) { into("${rootProject.name}-iceberg-rest-server") }
         from(projectDir.file("NOTICE.rest")) { into("${rootProject.name}-iceberg-rest-server") }
         from(projectDir.file("README.md")) { into("${rootProject.name}-iceberg-rest-server") }
-        from(projectDir.file("DISCLAIMER_WIP.txt")) { into("${rootProject.name}-iceberg-rest-server") }
+        from(projectDir.file("DISCLAIMER.txt")) { into("${rootProject.name}-iceberg-rest-server") }
         into(outputDir)
         rename { fileName ->
           fileName.replace(".rest", "")
@@ -686,7 +686,7 @@ tasks {
         from(projectDir.file("LICENSE.trino")) { into("${rootProject.name}-trino-connector") }
         from(projectDir.file("NOTICE.trino")) { into("${rootProject.name}-trino-connector") }
         from(projectDir.file("README.md")) { into("${rootProject.name}-trino-connector") }
-        from(projectDir.file("DISCLAIMER_WIP.txt")) { into("${rootProject.name}-trino-connector") }
+        from(projectDir.file("DISCLAIMER.txt")) { into("${rootProject.name}-trino-connector") }
         into(outputDir)
         rename { fileName ->
           fileName.replace(".trino", "")

clients/client-python/MANIFEST.in

@@ -21,6 +21,6 @@ include requirements-dev.txt
 include README.md
 include LICENSE
 include NOTICE
-include DISCLAIMER_WIP.txt
+include DISCLAIMER.txt
 include gravitino/version.ini
 graft licenses

clients/client-python/build.gradle.kts

@@ -285,7 +285,7 @@ tasks {
       generatePypiProjectHomePage()
       delete("dist")
       copy {
-        from("${project.rootDir}/DISCLAIMER_WIP.txt") { into("./") }
+        from("${project.rootDir}/DISCLAIMER.txt") { into("./") }
         into("${project.rootDir}/clients/client-python")
         rename { fileName ->
           fileName.replace(".bin", "")
@@ -298,7 +298,7 @@ tasks {
 
     doLast {
       delete("README.md")
-      delete("DISCLAIMER_WIP.txt")
+      delete("DISCLAIMER.txt")
     }
   }