chore(build): update fess-parent to 15.5.0 and extend EOL date (#3039)

Update fess-parent version from 15.5.0-SNAPSHOT to 15.5.0 release
and extend end-of-life date from June 2027 to August 2027.

Author: marevol

pom.xml

@@ -40,7 +40,7 @@
 	<parent>
 		<groupId>org.codelibs.fess</groupId>
 		<artifactId>fess-parent</artifactId>
-		<version>15.5.0-SNAPSHOT</version>
+		<version>15.5.0</version>
 		<relativePath />
 	</parent>
 	<properties>

src/main/java/org/codelibs/fess/helper/SystemHelper.java

@@ -173,7 +173,7 @@ public void init() {
             logger.debug("Initializing {}", this.getClass().getSimpleName());
         }
         final Calendar cal = Calendar.getInstance(TimeZone.getTimeZone("UTC"));
-        cal.set(2027, 6 - 1, 1); // EOL Date
+        cal.set(2027, 8 - 1, 1); // EOL Date
         eolTime = cal.getTimeInMillis();
         if (isEoled()) {
             logger.error("Your system is out of support. See https://fess.codelibs.org/eol.html");