Update minSdkVersion to 21 for task libraries.

PiperOrigin-RevId: 351905126

Author: xunkai55

tensorflow_lite_support/java/src/java/org/tensorflow/lite/task/text/AndroidManifest.xml

@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="utf-8"?>
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
     package="org.tensorflow.lite.task.text">
-  <uses-sdk android:minSdkVersion="19" android:targetSdkVersion="29"/>
+  <uses-sdk android:minSdkVersion="21" android:targetSdkVersion="29"/>
 </manifest>

tensorflow_lite_support/java/src/java/org/tensorflow/lite/task/vision/AndroidManifest.xml

@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="utf-8"?>
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
     package="org.tensorflow.lite.task.vision">
-  <uses-sdk android:minSdkVersion="19" android:targetSdkVersion="29"/>
+  <uses-sdk android:minSdkVersion="21" android:targetSdkVersion="29"/>
 </manifest>

tensorflow_lite_support/java/src/java/org/tensorflow/lite/task/vision/classifier/AndroidManifest.xml

@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="utf-8"?>
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
     package="org.tensorflow.lite.task.vision.classifier">
-  <uses-sdk android:minSdkVersion="19" android:targetSdkVersion="29"/>
+  <uses-sdk android:minSdkVersion="21" android:targetSdkVersion="29"/>
 </manifest>

tensorflow_lite_support/java/src/java/org/tensorflow/lite/task/vision/detector/AndroidManifest.xml

@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="utf-8"?>
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
     package="org.tensorflow.lite.task.vision.detector">
-  <uses-sdk android:minSdkVersion="19" android:targetSdkVersion="29"/>
+  <uses-sdk android:minSdkVersion="21" android:targetSdkVersion="29"/>
 </manifest>

tensorflow_lite_support/java/src/java/org/tensorflow/lite/task/vision/segmenter/AndroidManifest.xml

@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="utf-8"?>
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
     package="org.tensorflow.lite.task.vision.segmenter">
-  <uses-sdk android:minSdkVersion="19" android:targetSdkVersion="29"/>
+  <uses-sdk android:minSdkVersion="21" android:targetSdkVersion="29"/>
 </manifest>