THRIFT-5562: remove gradle wrapper and use installed gradle 6.9
Client: java
Patch: Jiayu Liu

This closes #2576
diff --git a/lib/java/README.md b/lib/java/README.md
index c8ec1c3..f18f7dd 100644
--- a/lib/java/README.md
+++ b/lib/java/README.md
@@ -44,7 +44,7 @@
 
 To compile the Java Thrift libraries, simply do the following:
 
-    ./gradlew
+    gradle
 
 Yep, that's easy. Look for libthrift-<version>.jar in the build/libs directory.
 
@@ -65,12 +65,12 @@
 
 To just build the library without running unit tests you simply do this.
 
-    ./gradlew assemble
+    gradle assemble
 
 To install the library in the local Maven repository location
 where other Maven or Gradle builds can reference it simply do this.
 
-    ./gradlew install
+    gradle install
 
 The library will be placed in your home directory under .m2/repository
 
@@ -80,7 +80,7 @@
 
 Build Thrift behind a proxy:
 
-    ./gradlew -Dhttp.proxyHost=myproxyhost -Dhttp.proxyPort=8080 -Dhttp.proxyUser=thriftuser -Dhttp.proxyPassword=topsecret
+    gradle -Dhttp.proxyHost=myproxyhost -Dhttp.proxyPort=8080 -Dhttp.proxyUser=thriftuser -Dhttp.proxyPassword=topsecret
 
 or via
 
@@ -107,7 +107,7 @@
 
 The following command will build, unit test, and generate Clover reports:
 
-    ./gradlew -PcloverEnabled=true
+    gradle -PcloverEnabled=true
 
 
 Publishing Maven Artifacts to Maven Central
@@ -146,7 +146,7 @@
 With the key information and credentials in place the following will generate
 if needed the build artifacts and proceed to publish the results.
 
-    ./gradlew -Prelease=true uploadArchives
+    gradle -Prelease=true uploadArchives
 
 It is also possible to override the target repository for the Maven Publication
 by using a Gradle property, for example you can publish signed JAR files to your
@@ -157,7 +157,7 @@
 
 Or the same on the command line:
 
-    ./gradlew -Pmaven-repository-url=https://my.company.com/service/local/staging/deploy/maven2 -Prelease=true -Pthrift.version=0.11.0 uploadArchives
+    gradle -Pmaven-repository-url=https://my.company.com/service/local/staging/deploy/maven2 -Prelease=true -Pthrift.version=0.11.0 uploadArchives
 
 
 Dependencies
@@ -175,7 +175,7 @@
 
 * Per THRIFT-4805, TSaslTransportException has been removed. The same condition
 is now covered by TTansportException, where `TTransportException.getType() == END_OF_FILE`.
- 
+
 ## 0.12.0
 
 The access modifier of the AutoExpandingBuffer class has been changed from