Add x86_64-linux to Gemfile.lock

[julianguyen]

Description

We need to add x86_64-linux to platforms in Gemfile.lock for the Heroku deploy build to work.

The following error occurs:

remote: -----> Installing dependencies using bundler 2.3.25        
remote:        Running: BUNDLE_WITHOUT='development:test' BUNDLE_PATH=vendor/bundle BUNDLE_BIN=vendor/bundle/bin BUNDLE_DEPLOYMENT=1 bundle install -j4        
remote:        Your bundle only supports platforms ["aarch64-linux", "arm64-darwin-21",        
remote:        "arm64-darwin-22", "x86_64-darwin-20"] but your local platform is x86_64-linux.        
remote:        Add the current platform to the lockfile with        
remote:        `bundle lock --add-platform x86_64-linux` and try again.        
remote:        Bundler Output: Your bundle only supports platforms ["aarch64-linux", "arm64-darwin-21",        
remote:        "arm64-darwin-22", "x86_64-darwin-20"] but your local platform is x86_64-linux.        
remote:        Add the current platform to the lockfile with        
remote:        `bundle lock --add-platform x86_64-linux` and try again.        
remote:         
remote:  !        
remote:  !     Failed to install gems via Bundler.        
remote:  !        
remote:  !     Push rejected, failed to compile Ruby app.        
remote: 
remote:  !     Push failed        
remote: Verifying deploy...        
remote: 
remote: !	Push rejected to ifme.

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