docs: list v1.3.1 of the PHP sdk as first compatible w/adv constr.

While 1.3 _does_ contain the advanced operators, it'll still break if
it doesn't recognize the operators or if you provide an invalid semver
version. 1.3.1 fixes this, so we should try and nudge people towards
that instead.

website/docs/sdks/index.md

@@ -76,7 +76,7 @@ If you see an item marked with a ❌ that you would find useful, feel free to re
 | Basic support                                                                                                                                  | ✅                     | ✅                        | ✅                 | ✅                         | ✅                     | ✅                        | ✅                   | ✅                                                     |                                   |
 | <span id="strategy-constraints">**Category: [Strategy constraints](../advanced/strategy_constraints)**</span>                                  |                        |                           |                    |                            |                        |                           |                      |                                                        |                                   |
 | Basic support (`IN`, `NOT_IN` operators)                                                                                                       | ✅                     | ✅                        | ✅                 | ✅                         | ✅                     | ✅                        | ✅                   | ✅                                                     |                                   |
-| <span id="strategy-constraints-advanced-support">Advanced support (Semver, date, numeric and extended string operators)</span> (introduced in) | ✅ (5.1)               | ✅ (3.12)                 | ✅ (3.3)           | ✅ (5.1)                   | ✅ (4.2)               | ⭕                        | ✅ (1.3)             | ⭕                                                     | ✅ (0.8)                          |
+| <span id="strategy-constraints-advanced-support">Advanced support (Semver, date, numeric and extended string operators)</span> (introduced in) | ✅ (5.1)               | ✅ (3.12)                 | ✅ (3.3)           | ✅ (5.1)                   | ✅ (4.2)               | ⭕                        | ✅ (1.3.1)           | ⭕                                                     | ✅ (0.8)                          |
 | **Category: [Unleash Context](../user_guide/unleash_context)**                                                                                 |                        |                           |                    |                            |                        |                           |                      |                                                        |                                   |
 | Static fields (`environment`, `appName`)                                                                                                       | ✅                     | ✅                        | ✅                 | ✅                         | ✅                     | ✅                        | ✅                   | ✅                                                     |                                   |
 | Defined fields                                                                                                                                 | ✅                     | ✅                        | ✅                 | ✅                         | ✅                     | ✅                        | ✅                   | ✅                                                     |                                   |