fix(app/env-vars): make key regex non-greedy to match on first equal sign

app/portainer/helpers/env-vars.js

@@ -1,6 +1,6 @@
 import _ from 'lodash-es';
 
-export const KEY_REGEX = /(.+)/.source;
+export const KEY_REGEX = /(.+?)/.source;
 export const VALUE_REGEX = /(.*)?/.source;
 
 const KEY_VALUE_REGEX = new RegExp(`^(${KEY_REGEX})\\s*=(${VALUE_REGEX})$`);