BaseTools: Remove duplicated words in C tools

In an effort to clean the documentation of the above
package, remove duplicated words.

Cc: Bob Feng <bob.c.feng@intel.com>
Cc: Liming Gao <gaoliming@byosoft.com.cn>
Reviewed-by: Bob Feng <bob.c.feng@intel.com>
Signed-off-by: Pierre Gondois <pierre.gondois@arm.com>

BaseTools/Source/C/GenFv/GenFv.c

@@ -299,7 +299,7 @@ Returns:
         return STATUS_ERROR;
       }
       if (TempNumber == 0) {
-        Error (NULL, 0, 1003, "Invalid option value", "Fv block size can't be be set to zero");
+        Error (NULL, 0, 1003, "Invalid option value", "Fv block size can't be set to zero");
         return STATUS_ERROR;
       }
       mFvDataInfo.FvBlocks[0].Length = (UINT32) TempNumber;