Fix surface tension physical type mapping #20681 - #20682

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hello
I am a student new to open source contribution. I was trying to understand the codebase and solve issues i could understand. I came across this issue and i could understand it clearly hence i choose to solve this.
What was wrong-
In pysical.py , it maps various units with physical types .
Surface tension ahs units N/m which is also J/m2
Old entry had W * m2 * Hz**-1 represnts jy( Jansky) which is spectral flux density .
Actually jy is W * m**-2 * Hz**-1 which can be also written as (dimensionally equal to ) J * m**-2 which is actually surface tension. But in old mapping : W * m2 * Hz-1 gives jy and hence gives surface tension unit as J* m**2 (dimensionally equal ) which is wrong . I corrected the mapping and added tests for the correct and incorrect units.

First of all, we need to check if this is a regression or a misunderstanding. Keeping PR closed for now.

Understood, thank you for clarifying!