ICU-21507 Removing unused class initializer code

ICUDebug seemed to check Java version whether it's 1.4 or higher. The code referencing the version is already gone. We also no longer support Java 1.3 runtime since long time ago. Remove the unused code checking Java version.
diff --git a/icu4j/main/classes/core/src/com/ibm/icu/impl/ICUDebug.java b/icu4j/main/classes/core/src/com/ibm/icu/impl/ICUDebug.java
index e5fdfab..e6099cf 100644
--- a/icu4j/main/classes/core/src/com/ibm/icu/impl/ICUDebug.java
+++ b/icu4j/main/classes/core/src/com/ibm/icu/impl/ICUDebug.java
@@ -8,8 +8,6 @@
  */
 package com.ibm.icu.impl;
 
-import com.ibm.icu.util.VersionInfo;
-
 public final class ICUDebug {
     private static String params;
     static {
@@ -28,55 +26,6 @@
         }
     }
 
-    public static final String javaVersionString = System.getProperty("java.version", "0");
-    public static final boolean isJDK14OrHigher;
-    public static final VersionInfo javaVersion;
-
-    public static VersionInfo getInstanceLenient(String s) {
-        // Extracting ASCII numbers up to 4 delimited by
-        // any non digit characters
-        int[] ver = new int[4];
-        boolean numeric = false;
-        int i = 0, vidx = 0;
-        while (i < s.length()) {
-            char c = s.charAt(i++);
-            if (c < '0' || c > '9') {
-                if (numeric) {
-                    if (vidx == 3) {
-                        // up to 4 numbers
-                        break;
-                    }
-                    numeric = false;
-                    vidx++;
-                }
-            } else {
-                if (numeric) {
-                    ver[vidx] = ver[vidx] * 10 + (c - '0');
-                    if (ver[vidx] > 255) {
-                        // VersionInfo does not support numbers
-                        // greater than 255.  In such case, we
-                        // ignore the number and the rest
-                        ver[vidx] = 0;
-                        break;
-                    }
-                } else {
-                    numeric = true;
-                    ver[vidx] = c - '0';
-                }
-            }
-        }
-
-        return VersionInfo.getInstance(ver[0], ver[1], ver[2], ver[3]);
-    }
-
-    static {
-        javaVersion = getInstanceLenient(javaVersionString);
-
-        VersionInfo java14Version = VersionInfo.getInstance("1.4.0");
-
-        isJDK14OrHigher = javaVersion.compareTo(java14Version) >= 0;
-    }
-
     public static boolean enabled() {
         return debug;
     }
@@ -109,23 +58,4 @@
         }
         return result;
     }
-
-//    static public void main(String[] args) {
-//        // test
-//        String[] tests = {
-//            "1.3.0",
-//            "1.3.0_02",
-//            "1.3.1ea",
-//            "1.4.1b43",
-//            "___41___5",
-//            "x1.4.51xx89ea.7f",
-//            "1.6_2009",
-//            "10-100-1000-10000",
-//            "beta",
-//            "0",
-//        };
-//        for (int i = 0; i < tests.length; ++i) {
-//            System.out.println(tests[i] + " => " + getInstanceLenient(tests[i]));
-//        }
-//    }
 }