Refactor README update workflow to be run on macos machine (#23033)

* Updated reamde current tech stack action to be run on macos to solve issues in the pipeline, updated README with script

* Corrected update reamde pipeline

---------

Co-authored-by: Filippo <fzazzeroni@mozilla.com>

Author: FilippoZazzeroni

.github/workflows/update_readme_current_tech_stack.yml

@@ -7,7 +7,7 @@ on:
 
 jobs:
     update_readme_with_current_stack:
-        runs-on: ubuntu-latest
+        runs-on: macos-latest
 
         steps:
             - name: Checkout code

update_readme_project_stack.sh

@@ -37,7 +37,8 @@ function sed_into_readme() {
 PROJECT_FIREFOX_FILE="firefox-ios/Client.xcodeproj/project.pbxproj"
 PROJECT_FOCUS_FILE="focus-ios/Blockzilla.xcodeproj/project.pbxproj"
 BIT_RISE_FILE="bitrise.yml"
-XCODE_VERSION=$(grep "stack:" $BIT_RISE_FILE | head -n 1 | grep -o '\d\d.\d')
+# Grepping the tail of Bitrise file since contains the correct Xcode version
+XCODE_VERSION=$(grep "stack:" $BIT_RISE_FILE | tail -n 1 | grep -o '\d\d.\d')
 DEPLOYMENT_TARGET_FIREFOX=$(deployment_target $PROJECT_FIREFOX_FILE)
 DEPLOYMENT_TARGET_FOCUS=$(deployment_target $PROJECT_FOCUS_FILE)
 README_FILE="README.md"