Update google-protobuf dependency that works with latest ruby versions

Gemfile.lock

@@ -1,8 +1,8 @@
 PATH
   remote: .
   specs:
-    lnrpc (0.11.1)
-      google-protobuf (>= 3.12)
+    lnrpc (0.13.0)
+      google-protobuf (>= 3.15.7)
       grpc (>= 1.28.0)
 
 GEM
@@ -40,4 +40,4 @@ DEPENDENCIES
   rspec (~> 3.0)
 
 BUNDLED WITH
-   2.1.4
+   2.2.23

README.md

@@ -5,13 +5,10 @@ a [gRPC](https://grpc.io/) client for [LND, the Lightning Network Daemon](https:
 
 ## Installation
 
-Note: there is still an GRPC/protobuf [issue with Ruby 2.7](https://github.com/protocolbuffers/protobuf/issues/7070).
-So lnrpc requires Ruby < 2.7.
-
 Add this line to your application's Gemfile:
 
 ```ruby
-gem 'lnrpc', '~> 0.11.0'
+gem 'lnrpc', '~> 0.13.0'
 ```
 lnrpc follows the lnd versioning, thus it is recommended to specify the exact version you need for your lnd node as dependency (see [#Versioning](#Versioning)).
 

lnrpc.gemspec

@@ -30,5 +30,5 @@ Gem::Specification.new do |spec|
   spec.add_development_dependency "rspec", "~> 3.0"
 
   spec.add_dependency "grpc", ">= 1.28.0"
-  spec.add_dependency "google-protobuf", ">=3.12"
+  spec.add_dependency "google-protobuf", ">=3.15.7"
 end