Inline .podspec.json extension definition

I noticed this because RuboCop barked at me for having a method with 11
SLOC instead of 10.

However, I'm happy with the change. The implementation expects the file
to be a JSON, so there's little value in making the extension
configurable. If we changed that var to `.podspec`, the implementation
would break!

ios-xcframework/Podfile

@@ -23,9 +23,7 @@ def setup_rnreanimated_pod_from_fork
 end
 
 def gutenberg_dependencies
-  podspec_extension = '.podspec.json'
-
-  Dir["../third-party-podspecs/*#{podspec_extension}"].each do |podspec_path|
+  Dir['../third-party-podspecs/*.podspec.json'].each do |podspec_path|
     pod_name = JSON.parse(File.read(podspec_path))['name']
 
     raise "Could not find pod name in JSON spec at #{podspec_path}" unless pod_name

ios-xcframework/Podfile.lock

@@ -665,6 +665,6 @@ SPEC CHECKSUMS:
   WordPress-Aztec-iOS: 7d11d598f14c82c727c08b56bd35fbeb7dafb504
   Yoga: f7decafdc5e8c125e6fa0da38a687e35238420fa
 
-PODFILE CHECKSUM: eed59291e8f65f4e532304d8e4091728b1906889
+PODFILE CHECKSUM: a240fb0d100c639b9b0bcedab219f9b0b51fbf0a
 
 COCOAPODS: 1.12.1