[clang-format] Correct indentation for `[key] = value,` entries in C# object initialisers

Restores content of commit cb3f20d2
reverted in commit 5a101f37
with a corrected commit message.

Summary: Do not use continuation indent for '[' in blocks in C# code.

Reviewers: krasimir

Reviewed By: krasimir

Subscribers: cfe-commits

Tags: #clang-format, #clang

Differential Revision: https://reviews.llvm.org/D75747