update v8 peer dependency range to match alpha releases

[djskinner]

Goal

Fix npm install error when installing @bugsnag/plugin-express version 8: No matching version found for @bugsnag/core@^8

$ npm i
npm WARN ERESOLVE overriding peer dependency
npm WARN While resolving: @bugsnag/plugin-express@8.0.0-alpha.3
npm WARN Found: @bugsnag/core@8.0.0-alpha.3
npm WARN node_modules/@bugsnag/core
npm WARN   @bugsnag/core@"^8.0.0-alpha.3" from @bugsnag/browser@8.0.0-alpha.3
npm WARN   node_modules/@bugsnag/browser
npm WARN     @bugsnag/browser@"^8.0.0-alpha.3" from @bugsnag/js@8.0.0-alpha.3
npm WARN     node_modules/@bugsnag/js
npm WARN   1 more (@bugsnag/node)
npm WARN 
npm WARN Could not resolve dependency:
npm WARN peer @bugsnag/core@"^8" from @bugsnag/plugin-express@8.0.0-alpha.3
npm WARN node_modules/@bugsnag/plugin-express
npm WARN   @bugsnag/plugin-express@"8.0.0-alpha.3" from the root project
npm WARN ERESOLVE overriding peer dependency
npm WARN While resolving: @bugsnag/plugin-express@8.0.0-alpha.3
npm WARN Found: @bugsnag/core@undefined
npm WARN node_modules/@bugsnag/core
npm WARN 
npm WARN Could not resolve dependency:
npm WARN peer @bugsnag/core@"^8" from @bugsnag/plugin-express@8.0.0-alpha.3
npm WARN node_modules/@bugsnag/plugin-express
npm WARN   @bugsnag/plugin-express@"8.0.0-alpha.3" from the root project
npm ERR! code ETARGET
npm ERR! notarget No matching version found for @bugsnag/core@^8.
npm ERR! notarget In most cases you or one of your dependencies are requesting
npm ERR! notarget a package version that doesn't exist.

Before:

After:

Testing:

• publish a new alpha release to confirm issue is resolved

[github-actions]

@bugsnag/browser bundle size diff

	Minified	Minfied + Gzipped
Before	44.74 kB	13.64 kB
After	44.74 kB	13.64 kB
±	No change	No change

code coverage diff

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