fix typo in ScopeGuard docs

Reviewed By: yfeldblum

Differential Revision: D15452123

fbshipit-source-id: 4ceec36f007e10284e8ac0482018099c7cea94d9

folly/ScopeGuard.h

@@ -140,7 +140,7 @@ using ScopeGuardImplDecay = ScopeGuardImpl<typename std::decay<F>::type, INE>;
 /**
  * ScopeGuard is a general implementation of the "Initialization is
  * Resource Acquisition" idiom.  Basically, it guarantees that a function
- * is executed upon leaving the currrent scope unless otherwise told.
+ * is executed upon leaving the current scope unless otherwise told.
  *
  * The makeGuard() function is used to create a new ScopeGuard object.
  * It can be instantiated with a lambda function, a std::function<void()>,