[lldb][Docs] Update bug report and code review links

The issues link as it was was including PRs, so I've made that
issues only and only those in an open state.

Code review is now on Gtihub so same thing, PRs only, open state,
label lldb.

Author: DavidSpickett

lldb/docs/index.rst

@@ -166,5 +166,5 @@ interesting areas to contribute to lldb.
    Releases <https://github.com/llvm/llvm-project/releases>
    Discussion Forums <https://discourse.llvm.org/c/subprojects/lldb/8>
    Developer Policy <https://llvm.org/docs/DeveloperPolicy.html>
-   Bug Reports <https://github.com/llvm/llvm-project/issues/labels/lldb/>
-   Code Reviews <https://reviews.llvm.org>
+   Bug Reports <https://github.com/llvm/llvm-project/issues?q=is%3Aissue+label%3Alldb+is%3Aopen>
+   Code Reviews <https://github.com/llvm/llvm-project/pulls?q=is%3Apr+label%3Alldb+is%3Aopen>