Fix downloading prebuilt hermes from the Github release (#33935)

Summary:
This:
```ruby
source[:http] = `https://github.com/facebook/react-native/releases/download/v#{version}/hermes-runtime-darwin-v#{version}.tar.gz`
```
currently fails with the following error:
```
[!] Failed to load 'hermes-engine' podspec:
[!] Invalid `hermes-engine.podspec` file: No such file or directory - https://github.com/facebook/react-native/releases/download/v0.69.0-rc.4/hermes-runtime-darwin-v0.69.0-rc.4.tar.gz.
```

For some reasons, the string with backticks is treated differently than with double quotes since this works:
```ruby
source[:http] = "https://github.com/facebook/react-native/releases/download/v#{version}/hermes-runtime-darwin-v#{version}.tar.gz"
```

## Changelog

<!-- Help reviewers and the release process by writing your own changelog entry. For an example, see:
https://github.com/facebook/react-native/wiki/Changelog
-->

[Internal] - Fix downloading prebuilt hermes from the Github release

Pull Request resolved: #33935

Test Plan:
- `npx react-native init RN069RC4 --version 0.69.0-rc.4`
- in the created project, run `pod install` with hermes enabled
- run `git init && git add . && git commit -m "Initial commit" && git remote add origin https://github.com/fortmarek/some-fake-repository` (this is necessary due to an unrelated bug in the RC4)
- observe error
- update `node_modules/react-native/sdks/hermes-engine/hermes-engine.podspec` with the change from this commit
- run `pod install`
- 🎉

Reviewed By: dmitryrykun

Differential Revision: D36775047

Pulled By: cortinico

fbshipit-source-id: 3772adca32fe9898cde33c187d19b7b181af3677

sdks/hermes-engine/hermes-engine.podspec

@@ -21,7 +21,7 @@ if version == '1000.0.0'
   source[:git] = git
   source[:commit] = `git ls-remote https://github.com/facebook/hermes main | cut -f 1`.strip
 else
-  source[:http] = `https://github.com/facebook/react-native/releases/download/v#{version}/hermes-runtime-darwin-v#{version}.tar.gz`
+  source[:http] = "https://github.com/facebook/react-native/releases/download/v#{version}/hermes-runtime-darwin-v#{version}.tar.gz"
 end
 
 module HermesHelper