UI: Fix typo in exec button URL-generation

[backspace]

This closes #8422, another bug facilitated by the difficulty
of automated testing when opening another window. Thanks to
@notnoop for narrowing this down.

[github-actions]

Ember Asset Size action

As of 81e7006

Files that got Bigger 🚨:

File	raw	gzip
nomad-ui.js	+6 B	+1 B

Files that stayed the same size 🤷‍:

File	raw	gzip
vendor.js	0 B	0 B
nomad-ui.css	0 B	0 B
vendor.css	0 B	0 B

[github-actions]

Ember Test Audit comparison

	master	81e7006	change
passes	1289	1289	0
failures	0	0	0
flaky	0	0	0
duration	5m 40s 994ms	6m 05s 833ms	+24s 839ms

[github-actions]

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