Remove conflicting parameter "a" from WMService dump

The parameter "a" was simultaneously declared as short version for
the parameters "animator" and for "all".

Due to the If-Else chain the parameter parameter was equivalent to
"animator" and not "all".

Test: Run "adb shell dumpsys window a". Check if it dumps the animator
content. To dump all content use "adb shell dumpsys window all".

Change-Id: Icc8a53c74e565cfc012284418798812b8206919e