Update docs/src/index.md

Co-authored-by: Nick Robinson <npr251@gmail.com>

Author: oxinabox

docs/src/index.md

@@ -10,8 +10,8 @@ For information about ChainRules, including how to write rules, refer to the gen
 [![](https://img.shields.io/badge/docs-stable-blue.svg)](https://JuliaDiff.github.io/ChainRulesCore.jl/stable)
 
 ## Testing Method Table Sensibility
-A basic feature of ChainRulesTestUtils is it's ability to check that the method table for `rrule` and `frule` remains sensible.
-This searches the method table for methods that should not exist and when it fails tells you where they were defined.
+A basic feature of ChainRulesTestUtils is its ability to check that the method tables for `rrule` and `frule` remain sensible.
+This searches the method tables for methods that should not exist and when it fails tells you where they were defined.
 By calling [`test_method_tables_sensibility`](@ref) ChainRulesTestUtils will check for things such as having attracted a rule to `DataType` rather than attaching it to a constructor.
 Basically all packages using ChainRulesTestUtils can use [`test_method_tables_sensibility`](@ref), as it is independent of what rules you have written.