update code block syntax for XML in headless-js-android documentation (facebook#4419)

Author: clicktodev

docs/headless-js-android.md

@@ -96,7 +96,7 @@ class MyTaskService : HeadlessJsTaskService() {
 
 Then add the service to your `AndroidManifest.xml` file inside the `application` tag:
 
-```
+```xml
 <service android:name="com.example.MyTaskService" />
 ```
 

website/versioned_docs/version-0.70/headless-js-android.md

@@ -96,7 +96,7 @@ class MyTaskService : HeadlessJsTaskService() {
 
 Then add the service to your `AndroidManifest.xml` file:
 
-```
+```xml
 <service android:name="com.example.MyTaskService" />
 ```
 

website/versioned_docs/version-0.71/headless-js-android.md

@@ -96,7 +96,7 @@ class MyTaskService : HeadlessJsTaskService() {
 
 Then add the service to your `AndroidManifest.xml` file:
 
-```
+```xml
 <service android:name="com.example.MyTaskService" />
 ```
 

website/versioned_docs/version-0.72/headless-js-android.md

@@ -96,7 +96,7 @@ class MyTaskService : HeadlessJsTaskService() {
 
 Then add the service to your `AndroidManifest.xml` file:
 
-```
+```xml
 <service android:name="com.example.MyTaskService" />
 ```
 

website/versioned_docs/version-0.73/headless-js-android.md

@@ -96,7 +96,7 @@ class MyTaskService : HeadlessJsTaskService() {
 
 Then add the service to your `AndroidManifest.xml` file inside the `application` tag:
 
-```
+```xml
 <service android:name="com.example.MyTaskService" />
 ```
 

website/versioned_docs/version-0.74/headless-js-android.md

@@ -96,7 +96,7 @@ class MyTaskService : HeadlessJsTaskService() {
 
 Then add the service to your `AndroidManifest.xml` file inside the `application` tag:
 
-```
+```xml
 <service android:name="com.example.MyTaskService" />
 ```
 

website/versioned_docs/version-0.75/headless-js-android.md

@@ -96,7 +96,7 @@ class MyTaskService : HeadlessJsTaskService() {
 
 Then add the service to your `AndroidManifest.xml` file inside the `application` tag:
 
-```
+```xml
 <service android:name="com.example.MyTaskService" />
 ```
 

website/versioned_docs/version-0.76/headless-js-android.md

@@ -96,7 +96,7 @@ class MyTaskService : HeadlessJsTaskService() {
 
 Then add the service to your `AndroidManifest.xml` file inside the `application` tag:
 
-```
+```xml
 <service android:name="com.example.MyTaskService" />
 ```