[macOS] Bump minimum macOS support to 10.14

Flutter 3.3 was the last stable release to support macOS 10.11 through
10.13. As of Flutter 3.7, the minimum supported version of macOS is
10.14 (Mojave). This should have landed with the release rollout, but I
missed updating the website.

RFC: https://flutter.dev/go/flutter-drop-macOS-10.13-2022-q4

Issue: flutter/flutter#114445

src/development/tools/sdk/release-notes/supported-platforms.md

@@ -31,7 +31,7 @@ Flutter supports the following platforms as part of Google-tested and best-effor
 |Android | API 16 (Android 4.1) & above | All     |
 |iOS     | iOS 11 & above               | All     |
 |Linux   | Debian, 64-bit               | All     |
-|macOS   | El Capitan (10.11) & above   | All     |
+|macOS   | Mojave (10.14) & above       | All     |
 |Web     | Chrome 84  & above           | All     |
 |Web     | Firefox 72.0 & above         | All     |
 |Web     | Safari on El Capitan & above | All     |
@@ -76,16 +76,13 @@ and stable channels.
 |Linux   |Debian 9 & below    |
 |Linux   |Ubuntu 20.04        |
 |Linux   |Ubuntu 22.04 (Aspirational Google-tested platform)        |
-|macOS   |El Capitan (10.11) - Big Sur (11)*   |
+|macOS   |Mojave (10.14) - Big Sur (11)*   |
 |Windows |Windows 11 (Aspirational Google-tested platform)          |
 |Windows |Windows 8           |
 |Windows |Windows 7           |
 {:.table.table-striped}
 </div>
 
-\* Flutter 3.3 is the last stable release with macOS 10.11 through 10.13
-best-effort support.
-
 ### Unsupported platforms
 
 <div class="table-wrapper" markdown="1">
@@ -94,7 +91,7 @@ best-effort support.
 |Android |Android SDK 15 & below                      |
 |iOS     |[iOS 10 & below and `arm7v` 32-bit iOS][]   |
 |Linux   |Any 32-bit platform                         |
-|macOS   |Yosemite (10.10) & below                    |
+|macOS   |El Capitan (10.13) & below                    |
 |Windows |Windows Vista & below                       |
 |Windows |Any 32-bit platform                         |
 {:.table.table-striped}