Auto merge of #6452 - matthiaskrgr:bump_nightly, r=flip1995

bump pinned nightly from nightly-2020-12-09 to nightly-2020-12-14

This should hopefully fix incremental compilation ICEs in rustc that I have encountered multiple times while working with the previously pinned nightly.

changelog: none

Author: bors

rust-toolchain

@@ -1,3 +1,3 @@
 [toolchain]
-channel = "nightly-2020-12-09"
+channel = "nightly-2020-12-14"
 components = ["llvm-tools-preview", "rustc-dev", "rust-src", "rustfmt"]