Fix some documentation typos (ruby-grape#2217)

* Fix typos

* Remove hard wraps

CONTRIBUTING.md

@@ -119,7 +119,7 @@ Go back to your pull request after a few minutes and see whether it passed muste
 
 #### Be Patient
 
-It's likely that your change will not be merged and that the nitpicky maintainers will ask you to do more, or fix seemingly benign problems. Hang on there!
+It's likely that your change will not be merged and that the nitpicky maintainers will ask you to do more, or fix seemingly benign problems. Hang in there!
 
 #### Thank You
 

UPGRADING.md

@@ -27,7 +27,7 @@ declared(params, include_missing: false)
 # actual   => { b: '5' } (uncasted, unvalidated, <= 1.5.3)
 ```
 
-Another implication of this change is the dependent parameter resolution. Prior to 1.6.0 the following code produced an `Grape::Exceptions::UnknownParameter` because `:a` was replace by `:b`:
+Another implication of this change is the dependent parameter resolution. Prior to 1.6.0 the following code produced a `Grape::Exceptions::UnknownParameter` because `:a` was replaced by `:b`:
 
 ```ruby
 params do
@@ -47,7 +47,7 @@ See [#2189](https://github.com/ruby-grape/grape/pull/2189) for more information.
 #### Nil value and coercion
 
 Prior to 1.2.5 version passing a `nil` value for a parameter with a custom coercer would invoke the coercer, and not passing a parameter would not invoke it.
-This behavior was not tested or documented. Version 1.3.0 quietly changed this behavior, in such that `nil` values skipped the coercion. Version 1.5.3 fixes and documents this as follows:
+This behavior was not tested or documented. Version 1.3.0 quietly changed this behavior, in that `nil` values skipped the coercion. Version 1.5.3 fixes and documents this as follows:
 
 ```ruby
 class Api < Grape::API
@@ -197,13 +197,13 @@ end
 
 #### Nil values for structures
 
-Nil values always been a special case when dealing with types especially with the following structures:
+Nil values have always been a special case when dealing with types, especially with the following structures:
 
 - Array
 - Hash
 - Set
 
-The behavior for these structures has change through out the latest releases. For example:
+The behavior for these structures has changed throughout the latest releases. For example:
 
 ```ruby
 class Api < Grape::API