Trust Tokens: Flip the field trial testing config to 3P origin trial mode

As part of rolling out the Trust Tokens config change to use a third-party origin trial instead of the current nonstandard origin trial configuration, we're moving the main experiment group to serve the all-operations-require-origin-trial parameter instead of only-issuance-requires-origin-trial. To make this experiment config change, we first need to update the field trial testing config to use the new parameter value.

(This should be a no-op, since tests that care about this value currently set the parameter manually.)

Bug: 1154714
Change-Id: Iefcc10d9abd93bf924d27a1d2910defc8d5015f7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2610993Reviewed-by: Dan McArdle <dmcardle@chromium.org>
Commit-Queue: Dan McArdle <dmcardle@chromium.org>
Auto-Submit: David Van Cleve <davidvc@chromium.org>
Cr-Commit-Position: refs/heads/master@{#841083}

testing/variations/fieldtrial_testing_config.json

@@ -7614,7 +7614,7 @@
                 {
                     "name": "Enabled",
                     "params": {
-                        "TrustTokenOperationsRequiringOriginTrial": "only-issuance-requires-origin-trial"
+                        "TrustTokenOperationsRequiringOriginTrial": "all-operations-require-origin-trial"
                     },
                     "enable_features": [
                         "TrustTokens"