Docs: use 4-space indent in Java styleguide

This is a minor change to rewrite code snippets in
styleguide/java/java.md to use a 4-space indent for Java code snippets.
The codebase already uses a 4-space indent for actual Java code, so it
makes sense that our sample code should follow the real style.

We observed this inconsistency when reviewing
https://crrev.com/c/5447835.

Test: N/A
Change-Id: I76e186d0ce0935b9eb59a296e204a1c94f7913a6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5479839
Auto-Submit: Nate Fischer <ntfschr@chromium.org>
Reviewed-by: Andrew Grieve <agrieve@chromium.org>
Commit-Queue: Andrew Grieve <agrieve@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1291950}

styleguide/java/java.md

@@ -52,14 +52,14 @@ Avoid adding messages to exceptions that do not aid in debugging. For example:
 
 ```java
 try {
-  somethingThatThrowsIOException();
+    somethingThatThrowsIOException();
 } catch (IOException e) {
-  // Bad - message does not tell you more than the stack trace does:
-  throw new RuntimeException("Failed to parse a file.", e);
-  // Good - conveys that this block failed along with the "caused by" exception.
-  throw new RuntimeException(e);
-  // Good - adds useful information.
-  throw new RuntimeException(String.format("Failed to parse %s", fileName), e);
+    // Bad - message does not tell you more than the stack trace does:
+    throw new RuntimeException("Failed to parse a file.", e);
+    // Good - conveys that this block failed along with the "caused by" exception.
+    throw new RuntimeException(e);
+    // Good - adds useful information.
+    throw new RuntimeException(String.format("Failed to parse %s", fileName), e);
 }
 ```
 
@@ -97,8 +97,8 @@ import org.chromium.build.BuildConfig;
 ...
 
 if (BuildConfig.ENABLE_ASSERTS) {
-  // Any code here will be stripped in release builds by R8.
-  ...
+    // Any code here will be stripped in release builds by R8.
+    ...
 }
 ```
 
@@ -307,7 +307,7 @@ or
 
 ```java
 if (someConditional) {
-  return false;
+    return false;
 }
 ```
 
@@ -315,7 +315,7 @@ Do NOT do:
 
 ```java
 if (someConditional)
-  return false;
+    return false;
 ```
 
 ### Import Order