Revert "Disable libc-test for MIPS64 for now"

This reverts commit 6e719f7.

Author: JohnTitor

.github/workflows/bors.yml

@@ -116,9 +116,8 @@ jobs:
           i686-unknown-linux-musl,
           mips-unknown-linux-gnu,
           mips-unknown-linux-musl,
-          # FIXME: Disabled because of the `relocation truncated to fit` error
-          # mips64-unknown-linux-gnuabi64,
-          # mips64el-unknown-linux-gnuabi64,
+          mips64-unknown-linux-gnuabi64,
+          mips64el-unknown-linux-gnuabi64,
           mipsel-unknown-linux-musl,
           powerpc-unknown-linux-gnu,
           powerpc64-unknown-linux-gnu,