Fix unused-variable warning

The `fixedFpsMode` variable was being redeclared within an `else` block
in `CCodec.cpp`. This shadowed the variable declared in the parent
scope, causing the new local variable to be unused and triggering a
compiler warning.

This change removes the redundant `bool` type specifier, ensuring the
statement correctly assigns a new value to the existing variable
instead of creating a new one. This resolves the unused-variable
warning.

The change is generated by Gemini.

Test: presubmit
Bug: 315246135
Flag: EXEMPT, warning cleanup
Change-Id: I708bd9709c12569ac3c3a703bcffd3426d04cb72