Clean up E0712 explanation

diff --git a/src/librustc_error_codes/error_codes/E0712.md b/src/librustc_error_codes/error_codes/E0712.md
index 89f60084f0a60282c0e830da5b87f4beb8aec151..7e09210e7874cfad8ea9577ef12b2f1a8d1d6042 100644 (file)
--- a/src/librustc_error_codes/error_codes/E0712.md
+++ b/src/librustc_error_codes/error_codes/E0712.md
@@ -1,5 +1,5 @@
-This error occurs because a borrow of a thread-local variable was made inside a
-function which outlived the lifetime of the function.
+A borrow of a thread-local variable was made inside a function which outlived
+the lifetime of the function.
 
 Erroneous code example: