[folks] doc: Fix a typo in HACKING

[Philip Withnall <pwithnall src gnome org>]

commit 4bda16a913d00b44ada0111f89dfc6548a550625
Author: Philip Withnall <philip withnall collabora co uk>
Date:   Tue Jan 20 12:09:11 2015 +0000

    doc: Fix a typo in HACKING

 HACKING |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/HACKING b/HACKING
index 71e7d5a..387f8bc 100644
--- a/HACKING
+++ b/HACKING
@@ -74,7 +74,7 @@ Vala-specific rules
    C functions, but it's too late to change this (as it would make 'git blame'
    useless).
 
-5. Private and internal class data members should beging with a _ (public data
+5. Private and internal class data members should begin with a _ (public data
    members and local variables should not begin with a _). This is to make
    non-public data members instantly recognizable as such (which helps
    readability).