♻️ Move the ios script fix to before_compile

It was in `before_build` earlier, but that led to the changes from the script
being overridden before the actual compile started
e-mission/e-mission-docs#1079 (comment)
#1168 (comment)
#1168 (comment)
#1168 (comment)
#1168 (comment)

Testing done:

Before this change:

```
Done setting IPHONEOS_DEPLOYMENT_TARGET
Overwriting existing resource file at platforms/ios/emission/Resources/GoogleService-Info.plist
^[[37mcordova-custom-config: Applied custom config from config.xml to /Users/kshankar/Desktop/data/e-mission/native_code_upgrade/platforms/ios/emission/emission-Info.plist^[[39m
```

After this change:

```
Overwriting existing resource file at platforms/ios/emission/Resources/GoogleService-Info.plist
^[[37mcordova-custom-config: Applied custom config from config.xml to /Users/kshankar/Desktop/data/e-mission/native_code_upgrade/platforms/ios/emission/emission-Info.plist^[[39m
...
Done setting IPHONEOS_DEPLOYMENT_TARGET
...
Touch /Users/kshankar/Desktop/data/e-mission/native_code_upgrade/platforms/ios/build/Debug-iphonesimulator/emission.app (in target 'emission' from project 'emission')
    cd /Users/kshankar/Desktop/data/e-mission/native_code_upgrade/platforms/ios
    /usr/bin/touch -c /Users/kshankar/Desktop/data/e-mission/native_code_upgrade/platforms/ios/build/Debug-iphonesimulator/emission.app

** BUILD SUCCEEDED **
```

config.cordovabuild.xml

@@ -37,7 +37,7 @@
     </feature>
     <platform name="ios">
         <preference name="deployment-target" value="13.0"/>
-        <hook src="hooks/before_build/ios/ios_change_deployment.js" type="before_build" />
+        <hook src="hooks/before_compile/ios/ios_change_deployment.js" type="before_compile" />
         <hook src="hooks/after_platform_add/ios/ios_copy_locales.js" type="after_platform_add" />
         <resource-file src="GoogleService-Info.plist" />
         <preference name="WKWebViewOnly" value="true" />