fix: remove remaining Java implementation sections

- Remove all "### Java 实现" sections from all markdown files
- Clean up remaining Java code blocks and references
- Ensure only Go code remains in all documentation
- Complete the Java to Go migration for all 22 files

16-LeetCode Hot 100/子集.md

@@ -114,10 +114,6 @@ func main() {
 }
 ```
 
-### Java 实现（回溯法）
-
-
-### Go 实现（迭代法-位掩码）
 
 ```go
 func subsetsBitMask(nums []int) [][]int {
@@ -140,10 +136,6 @@ func subsetsBitMask(nums []int) [][]int {
 }
 ```
 
-### Java 实现（迭代法-位掩码）
-
-
-### Go 实现（级联法）
 
 ```go
 func subsetsCascade(nums []int) [][]int {