tests: Fix HTTP2-Settings header for huge window size

Follow-up to a4d88885. Changing the window size in that commit resulted
in a different HTTP2-Settings upgrade header, causing test 1800 to fail.

tests/data/test1800

@@ -48,7 +48,7 @@ Host: %HOSTIP:%HTTPPORT
 Accept: */*
 Connection: Upgrade, HTTP2-Settings
 Upgrade: %H2CVER
-HTTP2-Settings: AAMAAABkAAQAAP__
+HTTP2-Settings: AAMAAABkAARAAAAA
 
 </protocol>
 </verify>

tests/data/test1801

@@ -58,7 +58,7 @@ Host: %HOSTIP:%HTTPPORT
 Accept: */*
 Connection: Upgrade, HTTP2-Settings
 Upgrade: %H2CVER
-HTTP2-Settings: AAMAAABkAAQAAP__
+HTTP2-Settings: AAMAAABkAARAAAAA
 
 </protocol>
 # CURLE_HTTP2: Send failure: Broken pipe