fix typo in README.md

Summary:
```
s/safer to safer to log/safer to log/
```

Reviewed By: yfeldblum

Differential Revision: D17629820

fbshipit-source-id: 8f9c3e412dfe52664ac1ae45e521f7df8815cef1

folly/logging/README.md

@@ -106,8 +106,8 @@ and type-safe mechanisms for formatting log messages.
 
 ## Escapes unprintable characters in log messages by default.
 
-This makes it safer to safer to log arbitrary input data, without worrying if
-the data may contain potentially malicious terminal escape sequences.
+This makes it safer to log arbitrary input data, without worrying if the data
+may contain potentially malicious terminal escape sequences.
 
 For instance, this helps avoid vulnerabilities like CVE-2013-1862 and
 CVE-2009-4496.