preferences_processing.php: fix Cell Phone regex
preferences_processing.php: fix Cell Phone regex

Fix an error introduced in 84a75b15f6d4283f4b069f138173dd941914e28a.
An extra space caused the Cell Phone regex to match 3-24 spaces
instead of 3-24 numbers. This commit removes the erroneous space.

Curufir/smr,smrealms/smr,smrealms/smr,smrealms/smr,hemberger/smr,gamedevforks/smr,Curufir/smr,hemberger/smr,gamedevforks/smr,gamedevforks/smr,gamedevforks/smr,hemberger/smr,hemberger/smr,Curufir/smr