[clang-format] [PR41187] moves Java import statements to the wrong location if code...

[clang-format] [PR41187] moves Java import statements to the wrong location if code contains statements that start with the word import

Summary:
Import sorting of java file, incorrectly move import statement to after a function beginning with the word import.

Make 1 character change to regular expression to ensure there is always at least one space/tab after the word import

Previously clang-format --style="LLVM" would format

```
import X;

class C {
  void m() {
    importFile();
  }
}
```
as

```
class C {
  void m() {
    importFile();
import X;
  }
}
```

Reviewers: djasper, klimek, reuk, JonasToth

Reviewed By: klimek

Subscribers: cfe-commits

Tags: #clang-tools-extra

Differential Revision: https://reviews.llvm.org/D59684

llvm-svn: 357345