AXIS2-6103 Fix remaining initialWindowSize inconsistencies and invalid JSON samples

Address Gemini review findings:
- Update WildFly guide: http/https listener examples and summary table
  still had 131072 (128KB), now 2097152 (2MB)
- Update http2-integration-guide: protocol selection example had 32768,
  now 2097152
- Fix invalid JSON in Spring Boot userguide samples: unquoted string
  values and non-standard email domain (use user@example.org per RFC 2606)

Author: robertlazarski

src/site/xdoc/docs/http2-integration-guide.xml

@@ -226,7 +226,7 @@ modules/
 <transportSender name="h2" class="org.apache.axis2.transport.h2.impl.httpclient5.H2TransportSender">
     <parameter name="PROTOCOL">HTTP/2.0</parameter>
     <parameter name="maxConcurrentStreams">100</parameter>
-    <parameter name="initialWindowSize">32768</parameter>
+    <parameter name="initialWindowSize">2097152</parameter>
 </transportSender>
 </pre>
 

src/site/xdoc/docs/json-springboot-tomcat11-userguide.xml

@@ -454,7 +454,7 @@ curl -v -H "Content-Type: application/json" -X POST --data @login.dat http://loc
 Where the contents of login.dat are:
 </p>
 <pre>
-{"doLogin":[{"arg0":{"email":java-dev@axis.apache.org,"credentials":userguide}}]}
+{"doLogin":[{"arg0":{"email":"user@example.org","credentials":"userguide"}}]}
 </pre>
 <p>
 Response:

src/site/xdoc/docs/json-springboot-userguide.xml

@@ -355,7 +355,7 @@ curl -v -H "Content-Type: application/json" -X POST --data @login.dat http://loc
 Where the contents of login.dat are:
 </p>
 <pre>
-{"doLogin":[{"arg0":{"email":java-dev@axis.apache.org,"credentials":userguide}}]}
+{"doLogin":[{"arg0":{"email":"user@example.org","credentials":"userguide"}}]}
 </pre>
 <p>
 Response: 

src/site/xdoc/docs/wildfly-http2-integration-guide.xml

@@ -97,7 +97,7 @@ large-payload workloads. See
                        enable-http2="true"
                        http2-enable-push="false"
                        http2-header-table-size="8192"
-                       http2-initial-window-size="131072"
+                       http2-initial-window-size="2097152"
                        http2-max-concurrent-streams="75"
                        http2-max-frame-size="65536"
                        http2-max-header-list-size="32768"
@@ -116,7 +116,7 @@ large-payload workloads. See
                         enable-http2="true"
                         http2-enable-push="false"
                         http2-header-table-size="8192"
-                        http2-initial-window-size="131072"
+                        http2-initial-window-size="2097152"
                         http2-max-concurrent-streams="75"
                         http2-max-frame-size="65536"
                         http2-max-header-list-size="32768"
@@ -180,7 +180,7 @@ large-payload workloads. See
 <table border="1">
 <tr><th>Parameter</th><th>Production Value</th><th>Optimization Purpose</th></tr>
 <tr><td>buffer-size</td><td>65536 (64KB)</td><td>Aligned with Enhanced Moshi H2 processing</td></tr>
-<tr><td>http2-initial-window-size</td><td>131072 (128KB)</td><td>Optimized for 50MB+ JSON payloads</td></tr>
+<tr><td>http2-initial-window-size</td><td>2097152 (2MB)</td><td>Avoids flow-control round trips on large responses</td></tr>
 <tr><td>http2-max-frame-size</td><td>65536 (64KB)</td><td>Consistent buffer alignment across layers</td></tr>
 <tr><td>http2-max-concurrent-streams</td><td>75</td><td>Memory-constrained optimization</td></tr>
 <tr><td>receive-buffer</td><td>4194304 (4MB)</td><td>Large payload handling</td></tr>