Replace 'his or her' with their for #inclusivefixit

Test: treehugger
Change-Id: I2cdced1bc73630b50f9c6b843ec5539a840371ff
diff --git a/README.rst b/README.rst
index a6db1f1..f81eaa7 100644
--- a/README.rst
+++ b/README.rst
@@ -16,9 +16,9 @@
   performance *at the same time*. libbcc attempts to address these
   design constraints.
 
-* it supports on-device linking. Each device vendor can supply his or
-  her own runtime bitcode library (lib*.bc) that differentiates his or
-  her system. Specialization becomes ecosystem-friendly.
+* it supports on-device linking. Each device vendor can supply their
+  own runtime bitcode library (lib*.bc) that differentiates their
+  system. Specialization becomes ecosystem-friendly.
 
 libbcc provides: