[FLINK-4289] Unset -x flag for .java files

Some source files had the -x flag set:

Before this change:
```
$ find . -perm +111 -type f | grep "\.java"
./flink-contrib/flink-tweet-inputformat/src/main/java/org/apache/flink/contrib/tweetinputformat/model/places/Attributes.java
./flink-contrib/flink-tweet-inputformat/src/main/java/org/apache/flink/contrib/tweetinputformat/model/places/BoundingBox.java
./flink-contrib/flink-tweet-inputformat/src/main/java/org/apache/flink/contrib/tweetinputformat/model/places/Places.java
./flink-contrib/flink-tweet-inputformat/src/main/java/org/apache/flink/contrib/tweetinputformat/model/tweet/Contributors.java
./flink-contrib/flink-tweet-inputformat/src/main/java/org/apache/flink/contrib/tweetinputformat/model/tweet/Coordinates.java
./flink-contrib/flink-tweet-inputformat/src/main/java/org/apache/flink/contrib/tweetinputformat/model/tweet/CurrentUserRetweet.java
./flink-contrib/flink-tweet-inputformat/src/main/java/org/apache/flink/contrib/tweetinputformat/model/tweet/entities/Entities.java
./flink-contrib/flink-tweet-inputformat/src/main/java/org/apache/flink/contrib/tweetinputformat/model/tweet/entities/HashTags.java
./flink-contrib/flink-tweet-inputformat/src/main/java/org/apache/flink/contrib/tweetinputformat/model/tweet/entities/Media.java
./flink-contrib/flink-tweet-inputformat/src/main/java/org/apache/flink/contrib/tweetinputformat/model/tweet/entities/Size.java
./flink-contrib/flink-tweet-inputformat/src/main/java/org/apache/flink/contrib/tweetinputformat/model/tweet/entities/Symbol.java
./flink-contrib/flink-tweet-inputformat/src/main/java/org/apache/flink/contrib/tweetinputformat/model/tweet/entities/URL.java
./flink-contrib/flink-tweet-inputformat/src/main/java/org/apache/flink/contrib/tweetinputformat/model/tweet/entities/UserMention.java
./flink-contrib/flink-tweet-inputformat/src/main/java/org/apache/flink/contrib/tweetinputformat/model/tweet/Tweet.java
./flink-contrib/flink-tweet-inputformat/src/main/java/org/apache/flink/contrib/tweetinputformat/model/User/Users.java
./flink-libraries/flink-gelly/src/main/java/org/apache/flink/graph/Graph.java
./flink-libraries/flink-gelly/src/main/java/org/apache/flink/graph/gsa/ApplyFunction.java
./flink-libraries/flink-gelly/src/main/java/org/apache/flink/graph/gsa/GatherFunction.java
./flink-libraries/flink-gelly/src/main/java/org/apache/flink/graph/gsa/GatherSumApplyIteration.java
./flink-libraries/flink-gelly/src/main/java/org/apache/flink/graph/gsa/Neighbor.java
./flink-libraries/flink-gelly/src/main/java/org/apache/flink/graph/gsa/SumFunction.java
./flink-libraries/flink-gelly/src/main/java/org/apache/flink/graph/library/GSAConnectedComponents.java
./flink-libraries/flink-gelly/src/main/java/org/apache/flink/graph/library/GSASingleSourceShortestPaths.java
./flink-libraries/flink-gelly-examples/src/main/java/org/apache/flink/graph/examples/GSASingleSourceShortestPaths.java
./flink-libraries/flink-gelly-examples/src/test/java/org/apache/flink/graph/test/GatherSumApplyITCase.java
./flink-runtime/src/main/java/org/apache/flink/runtime/executiongraph/ExecutionGraph.java
```

After this change:
```
$ find . -perm +111 -type f | grep "\.java"
```