Bump docs and compatibility checking for API Level 24.

Also, remove a `SubjectTest` workaround that became unnecessary not because of that bump but because of https://github.com/google/truth/commit/68d13aaddeb2bc29850fb13cba4654bf20197f22. (It involves `StringBuilder`, which doesn't become `Comparable` [until Android14 / API Level 34](https://developer.android.com/reference/java/lang/StringBuilder#compareTo%28java.lang.StringBuilder%29) ([before](https://cs.android.com/android/platform/superproject/+/android-13.0.0_r84:libcore/ojluni/src/main/java/java/lang/StringBuilder.java;l=79;drc=8b7796fe566e14dd434ea42aa69bfa32aee3b98e), [after](https://cs.android.com/android/platform/superproject/+/android-14.0.0_r1:libcore/ojluni/src/main/java/java/lang/StringBuilder.java;l=89;drc=026512bc686b4f40c0fa276298732618f769409a)).)

This `minSdkVersion` bump follows [other Google foundational libraries](https://issuetracker.google.com/issues/474169350), and we expect the bump itself to have no practical impact on users.

RELNOTES=Our Android `minSdkVersion` is now 24 (Nougat). This follows the minimum of Google's foundational Android libraries, and we expect it to have no practical impact on users.
PiperOrigin-RevId: 953631364

core/src/test/java/com/google/common/truth/SubjectTest.java

diff --git a/core/src/test/java/com/google/common/truth/SubjectTest.java b/core/src/test/java/com/google/common/truth/SubjectTest.java
index 397e944..f81a256 100644
--- a/core/src/test/java/com/google/common/truth/SubjectTest.java
+++ b/core/src/test/java/com/google/common/truth/SubjectTest.java
@@ -813,16 +813,10 @@
     "UnnecessaryStringBuilder", // We need a type that doesn't implement value-based equals().
   })
   public void disambiguationWithSameToString() {
-    /*
-     * We use `Object` instead of `StringBuilder` to force the compiler to choose that(Object) over
-     * that(Comparable): StringBuilder does not implement Comparable under Android Marshmallow, so
-     * the test would fail there at runtime.
-     */
-    Object stringBuilderAsObject = new StringBuilder("foo");
     AssertionError e =
         expectFailure(
             whenTesting ->
-                whenTesting.that(stringBuilderAsObject).isEqualTo(new StringBuilder("foo")));
+                whenTesting.that(new StringBuilder("foo")).isEqualTo(new StringBuilder("foo")));
     assertFailureKeys(e, "expected", "but was");
     assertFailureValue(e, "expected", "foo");
     assertFailureValue(

pom.xml

diff --git a/pom.xml b/pom.xml
index fb34361..4c8cce7 100644
--- a/pom.xml
+++ b/pom.xml
@@ -290,8 +290,8 @@
             <annotations>com.google.common.truth.IgnoreJRERequirement</annotations>
             <signature>
               <groupId>com.toasttab.android</groupId>
-              <artifactId>gummy-bears-api-23</artifactId>
-              <version>0.12.0</version>
+              <artifactId>gummy-bears-api-24</artifactId>
+              <version>0.15.0</version>
               <!-- TODO(cpovirk): In principle, it would make sense to *also* test compatibility with JDK 1.8, since Truth also has JRE users. -->
             </signature>
           </configuration>