Print whole credit counts without a decimal point

[vikrantwiz02]

The Grade Validation PDFs from the bulk export printed Units as 1.0, 3.0, 2.0 and the credit totals as 19.0.

_build_grade_validation_semesters casts every credit through float(), so 3 becomes 3.0, and the PDF printed str(c["credits"]) as it stood. JSON serialisation drops a trailing zero, which is why the on-screen preview was already correct and only the generated file showed it.

Added one helper that formats a credit the same way the client's fmtCredits already does — bare when the count is whole, one decimal when it is not, so a half-credit course still prints in full:

Value	Printed
3.0	3
19.0	19
1.5	1.5

Applied to the Units cell and to the three credit totals in the same table — Total Credits Earned, Semester Credits Earned and Total Registered Credits — since leaving 19.0 under a column of 1 3 2 would read as half-finished. SPI and CPI are untouched and keep their one decimal.

Checked against a student's full history: semester 1 now prints units 1 3 2 3 3 2 2 3 with totals 19 / 19, semester 2 3 3 2 4 3 with 15 / 34, semester 3 all 3 with 18 / 52.